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United States Patent6640248
JorgensenOctober 28, 2003
Title
Application-aware, quality of service (QoS) sensitive, media access control (MAC) layer
Abstract
An application aware, quality of service (QoS) sensitive, media access control (MAC) layer includes an application-aware resource allocator, where the resource allocator allocates bandwidth resource to an application based on an application type. The application type can be based on input from at least one of: a packet header; and an application communication to the MAC layer. The application communication includes: a communication between the application, running on at least one of a subscriber workstation and a host workstation, and the MAC layer, running on at least one of a subscriber CPE station and a wireless base station. The bandwidth resource is wireless bandwidth. The resource allocator schedules bandwidth resource to an IP flow. The IP flow includes at least one of: a transmission control protocol/internet protocol (TCP/IP) IP flow; and a user datagram protocol/internet protocol (UDP/IP) IP flow. The resource allocator in scheduling takes into account resource requirements of at least one of a source application and a destination application of an IP flow. The resource allocator takes into account IP flow identification information extracted from at least one packet header field. The bandwidth resource is wireless bandwidth. The resource allocator allocates switching resource to an application based on an application type. The application type is based on input from at least one of: packet header; and an application communication to the MAC layer. The application communication includes a communication between an application, running on at least one of a subscriber workstation and a host workstation, and the MAC layer, running on at least one of a subscriber CPE station and a wireless base station. The application communication includes a priority class of the IP flow.
Inventors:Jorgensen; Jacob W. (Folsom, CA)
Assignee:Malibu Networks, Inc. (El Dorado Hills, CA)
Appl. No.:349482
Filed:July 9, 1999
Current U.S. Class:709/226 709/229 709/235 370/328 370/338 709/223 
Field of Search:709/226,223-225,229,230,235,238,249,206,203,105,245,220 370/459,256,389,355,392,395.52,401,429,443,461,468,474,310.2
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Primary Examiner: Jean; Frantz B.
Attorney, Agent or Firm:Venable LLP Albrecht; Ralph P.
Parent Case Text


This application claims benefit of priority from U.S. Provisional Application entitled "Wireless Broadband Point-To-Multipoint Connectivity And Network Access," filed Jul. 10, 1998, U.S. Provisional Patent Application No. 60/092,452.

CROSS-REFERENCE TO OTHER APPLICATIONS

The following applications of common assignee contain common disclosure: U.S. Patent Application entitled "Transmission Control Protocol/Internet Protocol (TCP/EP) Packet-Centric Wireless Point to Multi-Point (PtMP) Transmission System Architecture," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,477. U.S. Patent Application entitled "Quality of Service (QoS)--Aware Wireless Point to Multi-Point (PtMP) Transmission System Architecture," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,480. U.S. Patent Application entitled "Method for Providing Dynamic Bandwidth Allocation Based on IP-Flow Characteristics in a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/350,126. U.S. Patent Application entitled "Method for Providing for Quality of Service (QoS)--Based Handling of IP-Flows in a Wireless Point to Multi-Point Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/350,118. U.S. Patent Application entitled "IP-Flow Identification in a Wireless Point to Multi-Point Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/347,856. U.S. Patent Application entitled "IP-Flow Characterization in a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/350,150. U.S. Patent Application entitled "IP-Flow Classification in a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/350,156. U.S. Patent Application entitled "IP-Flow Prioritization in a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,476. U.S. Patent Application entitled "Method of Operation for Providing for Service Level Agreement (SLA) Based Prioritization in a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/350,170. U.S. Patent Application entitled "Method for Transmission Control Protocol (TCP) Rate Control With Link-Layer Acknowledgments in a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,481. U.S. Patent Application entitled "Transmission Control Protocol/Internet Protocol (TCP/IP)--Centric QoS Aware Media Access Control (MAC) Layer in a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/350,159. U.S. Patent Application entitled "Use of Priority-Based Scheduling for the Optimization of Latency and Jitter Sensitive IP Flows in a Wireless Point to Multi-Point Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/347,857. U.S. Patent Application entitled "Time Division Multiple Access/Time Division Duplex (TDMA/TDD) Access Method for a Wireless Point to Multi-Point Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,475. U.S. Patent Application entitled "Reservation Based Prioritization Method for Wireless Transmission of Latency and Jitter Sensitive IP-Flows in a Wireless Point to Multi-Point Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,483. U.S. Patent Application entitled "Translation of Internet-Prioritized Internet Protocol (IP)-Flows into Wireless System Resource Allocations in a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,479. U.S. Patent Application entitled "Method of Operation for the Integration of Differentiated services (Diff-serv) Marked IP-Flows into a Quality of Service (QoS) Priorities in a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/350,162. U.S. Patent Application entitled "Method for the Recognition and Operation of Virtual Private Networks (VPNs) over a Wireless Point to Multi-Point (PtMP) Transmission System," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,975. U.S. Patent Application entitled "Time Division Multiple Access/Time Division Duplex (TDMA/TDD) Transmission Media Access Control (MAC) Air Frame," filed Jul. 9, 1999, U.S. application Ser. No. 09/350,173. U.S. Patent Application entitled "Transmission Control Protocol/Internet Protocol (TCP/IP) Packet-Centric Wireless Point to Point (PtP) Transmission System Architecture," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,478. U.S. Patent Application entitled "Transmission Control Protocol/Internet Protocol (TCP/IP) Packet-Centric Cable Point to Multi-Point (PtMP) Transmission System Architecture," filed Jul. 9, 1999, U.S. application Ser. No. 09/349,474.
Claims

What is claimed is:
1. An application aware, quality of service (QoS) sensitive, media access control (MAC) layer comprising: an application-aware resource allocator at the MAC layer, wherein said resource allocator allocates bandwidth resource to an internet protocol (IP) flow associated with a software application of a user based on IP QoS requirements of said software application, wherein said resource allocator allocates said bandwidth resource in a packet centric manner that is not circuit-centric and does not use asynchronous transfer mode (ATM).

2. The MAC layer according to claim 1, wherein said resource allocation is based on input from at least one of: a packet header; and a software application communication to said MAC layer.

3. The MAC layer according to claim 2, wherein said software application communication comprises: a communication between said software application, running on at least one of a subscriber workstation and a host workstation, and the MAC layer, running on at least one of a subscriber CPE station and a wireless base station.

4. The MAC layer according to claim 2, wherein said bandwidth resource comprises at least one of wide area network (WAN) wireless bandwidth and local area network (LAN) wireless bandwidth.

5. The MAC layer according to claim 1, wherein said resource allocator schedules said bandwidth resource to allow transmission of one or more packets of said IP flow.

6. The MAC layer according to claim 5, wherein said IP flow comprises at least one of: a transmission control protocol/internet protocol (TCP/IP) IP flow; and a user datagram protocol/internet protocol (UDP/IP) IP flow.

7. The MAC layer according to claim 5, wherein said resource allocator in said resource allocation takes into account resource requirements of at least one of a source application and a destination application of said IP flow.

8. The MAC layer according to claim 5, wherein said resource allocator takes into account IP flow identification information extracted from at least one packet header field.

9. The MAC layer according to claim 5, wherein said bandwidth resource is wireless bandwidth.

10. The MAC layer according to claim 1, wherein said resource allocator allocates switching resource to said software application based on an application type.

11. The MAC layer according to claim 10, wherein said application type is identified based on input from at least one of: packet header; and a software application communication to said MAC layer.

12. The MAC layer according to claim 11, wherein said software application communication comprises: a communication between said software application, running on at least one of a subscriber workstation and a host workstation, and said MAC layer, running on at least one of a subscriber CPE station and a wireless base station.

13. The MAC layer according to claim 11, wherein said software application communication comprises: a priority class of said IP flow.

14. The MAC layer according to claim 1, further comprising: an application identifier that identifies an application type of said software application to said resource allocator.

15. The MAC layer according to claim 14, wherein said application identifier uses contents of a packet header to identify a source application of said IP flow.

16. The MAC layer according to claim 14, wherein said application identifier uses a direct conduit of an application layer from a source application to identify said source application of said IP flow.

17. The MAC layer according to claim 1, wherein said application-aware resource allocator comprises a module operative to recognize an application type of said software application associated with said IP flow.

18. The MAC layer according to claim 17, wherein said module is operative to recognize said application type by analysis of applications above layer 4 of the OSI model.

19. The MAC layer according to claim 18, wherein said module is operative to recognize said application type by further analysis comprising analysis of at least one of: packet contents, packet header contents, packet payload contents, port numbers, information operated on at layer 3 of the OSI model, information operated on at layer 4 of the OSI model, information operated on at layer 5 of the OSI model, information operated on at layer 6 of the OSI model, and information operated on at layer 7 of the OSI model.

20. An application-aware media access control (MAC) layer for optimizing end user application internet protocol (IP) quality of service (QoS) to IP flows comprising: identifying means for identifying an application type of a software application associated with an IP flow; and allocating means for allocating resources to said IP flow, responsive to said identifying means, so as to optimize end user application IP QoS requirements of said software application, wherein said resource allocating means allocates resources in a packet-centric manner that is not circuit-centric and does not use asynchronous transfer mode (ATM).
Description
BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to telecommunications and, more particularly, to a system and method for implementing a QoS aware wireless point-to-multi-point transmission system.

2. Related Art

Telecommunication networks such as voice, data and video networks have conventionally been customized for the type of traffic each is to transport. For example, voice traffic is very latency sensitive but quality is less important, so voice networks are designed to transport voice traffic with limited latency. Traditional data traffic, such as, e.g., a spreadsheet, on the other hand is not latency sensitive, but error-free delivery is required. Conventional telecommunications networks use circuit switching to achieve acceptable end user quality of service (QoS). With the advent of new packet switching high bandwidth data networks, different types of traffic can be transported over a data network. Specifically, convergence of separate voice, data and video networks into a single broadband telecommunications network is enabled. To ensure end user satisfaction, a system is desired that provides QoS for various types of traffic to be transported.

Wireless networks present particular challenges over their wireline counterparts in delivering QoS. For example, wireless networks traditionally exhibit high bit error rates (BER) due to a number of reasons. Conventional wireless networks also implement circuit switched connections to provide reliable communications channels. However the use of circuit switched connections allocates bandwidth between communicating nodes whether or not traffic is constantly being transferred between the nodes. Therefore, circuit switched connections use communications bandwidth rather inefficiently.

Packet switching makes more efficient use of available bandwidth than does traditional circuit switching. Packet switching breaks up traffic into so-called "packets" which can then be transported from a source node to a destination for reassembly. Thus a particular portion of bandwidth can be shared by many sources and destinations yielding more efficient use of bandwidth.

A wireless broadband access telecommunications system is desired which can provide a QoS capability that is comparable to that delivered by wireline broadband access devices. Conventionally, one of the barriers to the deployment of wireless broadband access systems has been the absence of acceptable QoS characteristics, while at the same time delivering bandwidth sufficient to qualify as broadband. Delivery of raw bandwidth over wireless media without acceptable QoS would not benefit end users. Likewise, the delivery of a high level of QoS at the cost of sufficient bandwidth would also not benefit endusers.

Conventional efforts to provide wireless broadband access systems have not granted sufficient priority to QoS as a guiding principle in architecting the wireless systems, resulting in sub-optimal designs. With the rapid emergence of the Internet, the packet switching paradigm, and transmission control protocol/internet protocol (TCP/IP) as a universal data protocol, it has become clear that a new wireless system design has become necessary.

What is needed then is an IP-centric wireless broadband access system with true QoS capabilities.

SUMMARY OF THE INVENTION

The present invention is directed to an application aware, quality of service (QoS) sensitive, media access control (MAC) layer including an application-aware resource allocator, where the resource allocator allocates bandwidth resource to an application based on an application type.

The application type can be based on input from at least one of: a packet header; and an application communication to the MAC layer. The application communication includes: a communication between the application, running on at least one of a subscriber workstation and a host workstation, and the MAC layer, running on at least one of a subscriber customer premise equipment (CPE) station and a wireless base station. The bandwidth resource is wireless bandwidth.

The resource allocator schedules bandwidth resource to an IP flow. The IP flow includes at least one of: a transmission control protocol/internet protocol (TCP/IP) IP flow; and a user datagram protocol/internet protocol (UDP/IP) IP flow. The resource allocator in scheduling takes into account resource requirements of at least one of a source application and a destination application of an IP flow. The resource allocator takes into account IP flow identification information extracted from at least one packet header field. The bandwidth resource is wireless bandwidth.

The resource allocator allocates switching resource to an application based on an application type. The application type is based on input from at least one of: packet header; and an application communication to the MAC layer. The application communication includes a communication between an application, running on at least one of a subscriber workstation and a host workstation, and the MAC layer, running on at least one of a subscriber CPE station and a wireless base station. The application communication includes a priority class of the IP flow.

The MAC layer can further include an application identifier that identifies an application type to the resource allocator. The application identifier uses contents of a packet header to identify a source application of an IP flow. The application identifier uses a direct conduit of an application layer from a source application to identify the source application of an IP flow.

The cross-referenced applications listed above are incorporated herein by reference in their entireties.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will be described with reference to the accompanying figures, wherein:

FIG. 1A is a block diagram providing an overview of a standard telecommunications network providing local exchange carrier services within one or more local access and transport areas;

FIG. 1B depicts an exemplary network including workstations coupled to a data network;

FIG. 1C illustrates a conventional video network, such as for example a cable television (CATV) network;

FIG. 2A is a block diagram illustrating an overview of a standard telecommunications network providing both local exchange carrier and interexchange carrier services between subscribers located in different local access and transport areas;

FIG. 2B illustrates a signaling network in detail;

FIG. 2C illustrates an exemplary network carrying voice, data and video traffic over a data network;

FIG. 2D depicts a network including a point-to-multipoint wireless network coupled via a router to a data network;

FIG. 3A depicts an exemplary perspective diagram of a point-to-multipoint network;

FIG. 3B depicts a block diagram further illustrating a wireless point-to-multipoint network;

FIG. 4 depicts a wireless Internet protocol network access architecture of the present invention;

FIG. 5A depicts Internet protocol flows from a subscriber host to a wireless base station, and through a wireline connection to a destination host;

FIG. 5B illustrates a functional flow diagram including an example functional description of a transmission control protocol adjunct agent performing an outgoing transmission control protocol spoof function;

FIG. 5C illustrates a functional flow diagram including an exemplary functional description of a transmission control protocol adjunct agent performing an incoming transmission control protocol spoof function;

FIG. 6 illustrates a block diagram representing scheduling of mixed Internet protocol flows;

FIG. 7 illustrates packet header field information which can be used to identify Internet protocol flows and the quality of service requirements of the Internet protocol flows;

FIG. 8A is a block diagram summarizing an exemplary downlink analysis, prioritization and scheduling function;

FIG. 8B is a block diagram summarizing an exemplary uplink analysis prioritization and scheduling function;

FIG. 9 illustrates how a downlink flow scheduler can take into account a service level agreement in prioritizing a frame slot and scheduling resource allocation;

FIG. 10 depicts an embodiment of an inventive media access control hardware architecture;

FIG. 11 is an exemplary software organization for a packet-centric wireless point to multi-point telecommunications system;

FIG. 12A illustrates an exemplary time division multiple access media access control air frame;

FIG. 12B illustrates an exemplary structure for a time division multiple access/time division duplex air frame;

FIG. 12C illustrates an exemplary downstream transmission subframe;

FIG. 12D illustrates an exemplary upstream acknowledgment block field of a downstream transmission subframe;

FIG. 12E illustrates an exemplary acknowledgment request block field of a downstream transmission subframe;

FIG. 12F illustrates an exemplary frame descriptor block field of a downstream transmission subframe;

FIG. 12G illustrates an exemplary downstream media access control payload data unit of a downstream transmission subframe;

FIG. 12H illustrates an exemplary command and control block of a downstream transmission subframe;

FIG. 12I illustrates an exemplary upstream transmission subframe;

FIG. 12J illustrates an exemplary downstream acknowledgment block of an upstream transmission subframe;

FIG. 12K illustrates an exemplary reservation request block of an upstream transmission subframe 1204;

FIG. 12L illustrates an exemplary media access control payload data unit of an upstream transmission subframe;

FIGS. 12M, 12N and 12O illustrate an exemplary operations data block of an upstream transmission subframe;

FIG. 13 illustrates how an exemplary flow scheduler for the present invention functions;

FIG. 14 is an exemplary two-dimensional block diagram of an advanced reservation algorithm;

FIG. 15A is an exemplary logical flow diagram for a downlink flow analyzer;

FIG. 15B is an exemplary logical flow diagram for a downlink flow scheduler;

FIG. 16A is an exemplary logical flow diagram for an uplink flow analyzer;

FIG. 16B is an exemplary logical flow diagram for an uplink flow scheduler;

FIG. 17 illustrates Internet protocol flow in a downlink direction, including Internet protocol security encryption; and

FIG. 18 illustrates an uplink direction of Internet protocol security support.

In the figures, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The figure in which an element first appears is indicated by the leftmost digit(s) in the reference number.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

I. An Example Environment

The present invention is described in terms of an example environment. The example environment uses a fixed wireless point-to-multi-point (PtMP) connection to transmit packetized data information including for example, IP telephony, video, data, received from a telecommunications carrier. As used herein, a telecommunications carrier can include US domestic entities (see Definitions below at section II) such as, e.g., ILECs, CLECs, IXCs, NGTs and Enhanced Service Providers (ESPs), as well as global entities such as PTTs and NEs, recognized by those skilled in the art. In addition, as used herein a telecommunications system includes domestic systems used by entities such as, e.g., ILECs, CLECs, IXCs and Enhanced Service Providers (ESPs), as well as global systems recognized by those skilled in the art.

In the preferred embodiment, the traffic arrives from a wide area network (WAN) connection.

Data traffic is received from a data network through a network router and can be demodulated from internet protocol (IP) format to, for example, the point-to-point protocol (PPP). Network routers can include, for example, a general purpose computer, such as the SUN workstation running routing software or a dedicated routing device such as various models from CISCO of San Jose, Calif., ASCEND of Alameda, Calif., NETOPIA of Alameda, Calif., or 3COM of Santa Clara, Calif.,

In the alternative, a virtual private networking protocol, such as the point-to-point tunneling protocol (PPTP), can be used to create a "tunnel" between a remote user and a corporate data network. A tunnel permits a network administrator to extend a virtual private network from a server (e.g., a Windows NT server) to a data network (e.g., the Internet).

Although the invention is described in terms of this example environment, it is important to note that description in these terms is provided for purposes of illustration only. It is not intended that the invention be limited to this example environment or to the precise inter-operations between the above-noted devices. In fact, after reading the following description, it will become apparent to a person skilled in the relevant art how to implement the invention in alternative environments.

II. Definitions

Table 1 below defines common telecommunications terminology. These terms are used throughout the remainder of the description of the invention.

TABLE 1 Term Definition access tandem (AT) An AT is a class 3/4 switch used to switch calls between EOs in a LATA. An AT provides subscribers access to the IXCs, to provide long distance calling services. An access tandem is a network node. Other network nodes can include, for example, a CLEC, or other enhanced services provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral (IP). bearer (B) channels Bearer (B) channels are digital channels used to carry both digital voice and digital data information. An ISDN bearer channel is 64,000 bits per second, which can carry PCM-digitized voice or data. called party The called party is the caller receiving a call sent over a network at the destination or termination end. calling party The calling party is the caller placing a call over any kind of network from the origination end. central office (CO) A CO is a facility that houses an EO homed. EOs are often called COs. class 1 switch A class 1 switching office, the Regional Center (RC), is the highest level of local and long distance switching, or "office of last resort" to complete a call. class 3 switch A class 3 switching office was a Primary Center (PC); an access tandem (AT) has class 3 functionality. class 4 switch A class 4 switching office was a Toll Center (TC) if operators were present or else a Toll Point (TP); an access tandem (AT) has class 4 functionality. class 5 switch A class 5
switching office is an end office (EO) or the lowest level of local and long distance switching, a local central office. The switch closest to the end subscriber. competitive LEC CLECs are telecommunications services providers of local services (CLEC) that can compete with ILECs. !nterprise and Century 21 are examples. A CLEC may or may not handle IXC services as well. competitive access Teligent and Winstar are examples. providers (CAPS) customer premises CPE refers to devices residing on the premises of a customer and used equipment (CPE) to connect to a telephone network, including ordinary telephones, key telephone systems, PBXs, video conferencing devices and modems. digitized data (or Digitized data refers to analog data that has been sampled into a digital data) binary representation (i.e., comprising sequences of 0's and 1's). Digitized data is less susceptible to noise and attenuation distortions because it is more easily regenerated to reconstruct the original signal. egress end office The egress EO is the node or destination EO with a direct connection to the called party, the termination point. The called party is "homed" to the egress EO. egress Egress refers to the connection from a called party or termination at the destination end of a network, to the serving wire center (SWC). end office (EO) An EO is a class 5 switch used to switch local calls within a LATA. Subscribers of the LEC are connected ("homed") to EOs, meaning that EOs are the last switches to which the subscribers are connected. Enhanced Service A network services provider. Provider (ESP) equal access 1 + dialing as used in US domestic calling for access to any long distance carrier as required under the terms of the modified final judgment (MFJ) requiring divestiture of the Regional Bell Operating Companies (RBOCs) from their parent company, AT&T. global point of A GPOP refers to the location where international presence (GPOP) telecommunications facilities and domestic facilities interface, an international gateway POP. incumbent LEC ILECs are traditional LECs in the US, which are the Regional Bell (ILEC) Operating Companies (RBOCs). Bell South and US West are examples. ILEC can also stand for an independent LEC such as a GTE. ingress end office The ingress EO is the node or serving wire center (SVC) with a direct connection to the calling party, the origination point. The calling party is "homed" to the ingress EO. ingress Ingress refers to the connection from a calling party or origination. integrated service An ISDN Basic Rate Interface (BRI) line provides 2 bearer B digital network channels and 1 data D line (known as "2B + D" over one or two pairs) (ISDN) basic rate to a subscriber. interface (BRI) line integrated services ISDN is a network that provides a standard for communications digital network (voice, data and signaling), end-to-end digital transmission circuits, (ISDN) out-of-band signaling, and a features significant amount of bandwidth. inter machine trunk An inter-machine trunk (IMT) is a circuit between two commonly- (IMT) connected switches. inter-exchange IXCs are US domestic long distance telecommunications services carrier (IXC) providers. AT&T, MCI, Sprint, are examples. internet protocol (IP) IP is part of the TCP/IP protocols. It is used to recognize incoming messages, route outgoing messages, and keep track of Internet node addresses (using a number to specify a TCP/IP host on the Internet). IP corresponds to the network layer of OSI. Internet service An ISP is a company that provides Internet access to subscribers. provider (ISP) ISDN primary rate An ISDN Primary Rate Interface (PRI) line provides the ISDN interface (PRI) equivalent of a T1 circuit. The PRI delivered to a customer's premises can provide 23B + D (in North America) or 30B + D (in Europe) channels running at 1.544 megabits per second and 2.048 megabits per second, respectively. local exchange LECs are local telecommunications services providers. Bell Atlantic carrier (LEC) and US West are examples. local access and A LATA is a region in which a LEC offers services. There are over transport area 160 LATAs of these local geographical areas within the United States. (LATA) local area network A LAN is a communications network providing connections between (LAN) computers and peripheral devices (e.g., printers and modems) over a relatively short distance (e.g., within a building) under standardized control. modified final Modified final judgment (MFJ) was the decision requiring divestiture judgment (MFJ) of the Regional Bell Operating Companies (RBOCs) from their parent company, AT&T. network node A network node is a generic term for the resources in a telecommunications network, including switches, DACS, regenerators, etc. Network nodes essentially include all non-circuit (transport) devices. Other network nodes can include, for example, equipment of a CLEC, or other enhanced service provider (ESP), a point-of-presence (POP), an international gateway or global point-of- presence (GPOP). new entrant (NE) A new generation global telecommunications. next generation A new telecommunications services provider, especially IP telephony telephone (NGT) providers. Examples are Level 3 and Qwest. packetized voice or One example of packetized voice is voice over internet protocol voice over a (VOIP). Voice over packet refers to the carrying of telephony or backbone voice traffic over a data network, e.g. voice over frame, voice over ATM, voice over Internet Protocol (IP), over virtual private networks (VPNs), voice over a backbone, etc. Pipe or dedicated A pipe or dedicated communications facility connects an ISP to the communications internet. facility point of presence A POP refers to the location within a LATA where the IXC and LEC (POP) facilities interface. point-to-point A virtual private networking protocol, point-to-point tunneling tunneling protocol protocol (PPTP), can be used to create a "tunnel" between a remote (PPTP) user and a data network. A tunnel permits a network administrator to extend a virtual private network (VPN) from a server (e.g., a Windows NT server) to a data network (e.g., the Internet). point-to-point (PPP) PPP is a protocol permitting a computer to establish a connection with protocol the Internet using a modem. PPP supports high-quality graphical front ends, like Netscape. postal telephone State regulated telephone companies, many of which are being telegraph (PTT) deregulated. NTT is an example. private branch A PBX is a private switch located on the premises of a user. The user exchange (PBX) is typically a private company which desires to provide switching locally. private line with a A private line is a direct channel specifically dedicated to a customer's dial tone use between two specified points. A private line with a dial tone can connect a PBX or an ISP's access concentrator to an end office (e.g. a channelized T1 or PRI). A private line can also be known as a leased line. public switched The PSTN is the worldwide switched voice network. telephone network (PSTN) regional Bell RBOCs are the Bell operating companies providing LEC services operating companies after being divested from AT&T. (RBOCs) signaling system 7 SS7 is a type of common channel interoffice signaling (CCIS) used (SS7) widely throughout the world. The SS7
network provides the signaling functions of indicating the arrival of calls, transmitting routing and destination signals, and monitoring line and circuit status. switching hierarchy An office class is a functional ranking of a telephone central office or office switch depending on transmission requirements and hierarchical classification relationship to other switching centers. Prior to AT&T's divestiture of the RBOCs, an office classification was the number

assigned to offices according to their hierarchical function in the U.S. public switched network (PSTN). The following class numbers are used: class 1 = Regional Center (RC), class 2 = Sectional Center (SC), class 3 = Primary Center (PC), class 4 = Toll Center (TC) if operators are present or else Toll Point (TP), class 5 = End Office (EO) a local central office. Any one center handles traffic from one to two or more centers lower in the hierarchy. Since divestiture and with more intelligent software in switching offices, these designations have become less firm. The class 5 switch was the closest to the end subscriber. Technology has distributed technology closer to the end user, diffusing traditional definitions of network switching hierarchies and the class of switches. telecommunications A LEC, a CLEC, an IXC, an Enhanced Service Provider (ESP), an carrier intelligent peripheral (IP), an international/ global point-of-presence (GPOP), i.e., any provider of telecommunications services. transmission control TCP is an end-to-end protocol that operates at the transport and protocol (TCP) sessions layers of OSI, providing delivery of data bytes between processes running in host computers via separation and sequencing of IP packets. transmission control TCP/IP is a protocol that provides communications between protocol/internet interconnected networks. The TCP/IP protocol is widely used on the protocol (TCP/IP) Internet, which is a network comprising several large networks connected by high-speed connections. trunk A trunk connects an access tandem (AT) to an end office (EO). wide area network A WAN is a data network that extends a LAN over the circuits of a (WAN) telecommunications carrier. The carrier is typically a common carrier. A bridging switch or a router is used to connect the LAN to the WAN.

III. Introduction

A. Quality of Service (QOS) in a Wireless Environment

The concept of quality of service (QoS) is one of the most difficult and least understood topics in data networking. Although a common term in data networking, there are many different usages and definitions for QoS, leading to confusion regarding an exact meaning in precise or quantitative terms. Even further confusion is found when attempts are made to measure or specify numeric quantities sufficient to allow comparison of equipment or network performance with respect to QoS.

The confusion about QoS in general data networking is transferred and magnified when applied to wireless data communications. Wireless transmission has a higher inherent bit error rate (BER) than does wireline transmission. The addition of, e.g., a point-to-multipoint (PtMP) topology for multiple users sharing a wireless medium makes it desirable that QoS be defined in a manner that specifically addresses the multiple complicating factors in wireless data communications.

To provide a non-ambiguous definition of QoS that applies to wireless data communications, the nature of the problem that QoS is meant to solve is helpful. Many of the problems of data communications over wireless are unique and distinct from those of wireline data communications, while some are in fact shared. For wireless broadband access systems, the problems of quality delivery are somewhat more complex than for the wireline analog. Like its wireline counterpart, the problems encountered in wireless delivery of data include, e.g., slow peripheral access, data errors, "drop-outs," unnecessary retransmissions, traffic congestion, out-of-sequence data packets, latency, and jitter. In addition to these problems, wireless delivery adds problems including, e.g., high inherent bit error rates (BERs), limited bandwidth, user contention, radio interference, and TCP traffic rate management. A QoS-aware wireless system is desired to address all these problems.

There are a number of ways in which users or subscribers to a data network experience difficulties. One network difficulty is due to a lack of network availability. Depending on the access technology being used, this can include a "modem no-answer" condition, "network busy" condition, or a sudden unexpected "drop" of a network connection. These conditions would not be described as being consistent with high QoS. Once network connectivity is achieved, slow traffic caused by congestion, local access bottlenecks, and network failures can be experienced as slow web page loading, slow file transfers, or poor voice/video quality in streaming multimedia applications. Poor quality in streaming multimedia applications can instead result from high "jitter," or large and rapid variations in latency, leading to interruptions, distortion, or termination of session. Many different conditions can lead to actual data errors, which in some contexts can be catastrophic, such as in the file transfer of a spreadsheet. It is desirable that these problems of a data communications network be minimized or eliminated.

1. Quality

In data networking, quality usually implies the process of delivering data in a reliable and timely manner. What is reliable and timely is dependent on the nature of the traffic being addressed. These terms may include references to limitations in data loss, expectations of data accuracy, limitations of data latency variations (also known as jitter), and limitations of data retransmissions and limitations of data packet order inversions. Therefore, QoS is a complex concept, which can require a correspondingly complex mechanism to implement it.

QoS can be a relative term, finding different meanings for different users. A casual user doing occasional web browsing, but no file transfer protocol (FTP) file downloads or real time multimedia sessions may have different a different definition of QoS than a power user doing many FTP file downloads of large database or financial files, frequent H.323 video conferencing and IP telephony calls. Also, a user can pay a premium rate (i.e. a so-called service level agreement (SLA)) for high network availability, low latency, and low jitter, while another user can pay a low rate for occasional web surfing only, and on weekends only. Therefore, perhaps it is best to understand QoS as a continuum, defined by what network performance characteristic is most important to a particular user and the user's SLA. Maximizing the end-user experience is an essential component of providing wireless QoS.

2. Service

In data networking, a service can be defined as a type of connection from one end of a network to another. Formerly, this could have been further defined to be protocol specific, such as, e.g., IBM's systems network architecture (SNA), Novell's IPX, Digital's DECnet. However, it appears that TCP/IP (i.e. including user datagram protocol (UDP)) has evolved to become the overwhelming protocol of choice, and will continue to be in the foreseeable future. Therefore, service can be defined to be a particular type of TCP/IP connection or transmission. Such service types might include, e.g., FTP file transfers, e-mail traffic, hypertext transfer protocol (HTTP) traffic, H.323 videoconferencing sessions. It is desirable that a QoS mechanism deal with these differing types of service, in addition to dealing with the different types of quality as discussed previously.

3. QOS as a Mechanism

QoS can be thought of as a mechanism to selectively allocate scarce networking, transmission and communications resources to differentiated classes of network traffic with appropriate levels of priority. Ideally, the nature of the data traffic, the demands of the users, the conditions of the network, and the characteristics of the traffic sources and destinations all modify how the QoS mechanism is operating at any given instant. Ultimately, however, it is desirable that the QoS mechanism operate in a manner that provides the user with optimal service, in whatever manner the user defines it.

a. Circuit-Switched QoS

In legacy networks created primarily for voice traffic by telephone companies, data transmission was accomplished with reference to a circuit-centric definition of QoS. In this definition, QoS implied the ability to carry asynchronous (i.e. transmission of data through start and stop sequences without the use of a common clock) as well as isochronous (i.e. consistent timed access of network bandwidth for time-sensitive voice and video) traffic. Circuit-switched QoS was accomplished by dedicating an end-to-end circuit for each connection or service, whether it was voice (see FIG. 1A) or data. The circuit-centric QoS mechanism was simply the provision of this circuit for exclusive use by the user. Of course, this approach dedicates the circuit, all transmission channels associated with the circuit, and the transport media itself to a single user for the entire duration of the session, regardless of whether data is actually being transmitted every instant of the session. It was generally believed that only in this manner could true QoS be achieved. Therefore, traditional designs for wireless broadband access systems (see FIG. 2A) also used this approach, dedicating a wireless radio channel to each particular data connection, regardless of the application or whether indeed any data was being transmitted at any given moment. This circuit-centric approach to QoS is fairly expensive, in terms of the cost of the equipment, and the utilization factors for the transmission media itself.

b. Asynchronous Transfer Mode (ATM) QoS

With ATM networking, telephone companies could continue to provide a circuit-centric QoS mechanism with the establishment of permanent virtual connections (PVCs) (i.e. a virtual path or channel connection (VPC or VCC) provisioned for indefinite use) and switched virtual connections (SVCs) (i.e. a logical connection between endpoints established by an ATM network on demand based upon signaling messages received from the end user or another network) in an analogous manner to the legacy voice circuit mechanism. However, several new concepts were needed, including admission policy, traffic shaping, and mechanisms such as, e.g., leaky-buckets, in order to handle traffic that was now categorized as variable bit rate (VBR), constant bit rate (CBR), and unspecified bit rate (UBR).

Virtual circuits were to be established for data transmission sessions, again regardless of the data application or whether data was being transmitted at any given moment. Although ATM provides QoS for broadband network traffic, the underlying assumptions of ATM design include the low BER characteristic of wireline networks, not the high BER of the wireless medium. Without a recognition of the characteristics of the traffic that is being carried by the ATM mechanism and the high inherent BER of wireless, true QoS can not be provided. ATM QoS mechanisms do not address the unique challenges associated with wireless communication.

c. Packet-Switched QoS

Packet-switching is revolutionizing data communications, so conventional circuit-switch and ATM networking concepts and their legacy QoS mechanisms are in need of update. With packet-switched data communications, one cannot dedicate a circuit to a particular data communications session. Indeed, a strength of packet-switching lies in route flexibility and parallelism of its corresponding physical network. Therefore, the QoS mechanism cannot work in the same manner as the legacy circuit-centric QoS mechanism did.

Simply providing "adequate" bandwidth is not a sufficient QoS mechanism for packet-switched networks, and certainly not for wireless broadband access systems. Although some IP-flows are "bandwidth-sensitive," other flows are latency- and/or jitter-sensitive. Real time or multimedia flows and applications cannot be guaranteed timely behavior by simply providing excessive bandwidth, even if it were not cost-prohibitive to do so. It is desirable that QoS mechanisms for an IP-centric wireless broadband access system recognize the detailed flow-by-flow requirements of the traffic, and allocate system and media resources necessary to deliver these flows in an optimal manner.

d. Summary-QoS Mechanisms

Ultimately, the end-user experience is the final arbiter of QoS. It is desirable that an IP-centric wireless broadband access system assign and regulate system and media resources in a manner that can maximize the end-user experience. For some applications such as an initial screen of a Web page download, data transmission speed is the best measure of QoS. For other applications, such as the download or upload of a spreadsheet, the best measure of QoS can be the minimization of transmission error. For some applications, the best measure of QoS can be the optimization of both speed and error. For some applications, the timely delivery of packets can be the best measure of QoS. It is important to note that fast data transmission may not be the same as timely delivery of packets. For instance, data packets that are already "too old" can be transmitted rapidly, but by being too old can be of no use to the user. The nature of the data application itself and the desired end-user experience then can provide the most reliable criteria for the QoS mechanism. It is desired that an IP-centric wireless broadband access system provide a QoS mechanism that can dynamically optimize system behavior to each particular IP flow, and can also adapt to changes with changing network load, congestion and error rates.

4. Service Guarantees and Service Level Agreements (SLAs)

Service guarantees can be made and service level agreements (SLAs) can be entered into between a telecommunications service provider and a subscriber whereby a specified level of network availability can be described, and access charges can be based upon the specified level. Unfortunately, it is difficult to quantify the degree of network availability at any given time, and therefore this becomes a rather crude measure of service performance. It is desired that data delivery rate, error rate, retransmissions, latency, and jitter be used as measures of network availability, but measuring these quantities on a real-time basis can be beyond the capability of conventional network service providers (NSPs).

Another level of service discrimination desired by network service providers is a service level agreement (SLA) that provides for differing traffic rates, network availability, bandwidth, error rate, latency and jitter guarantees. It is desired that an IP-centric wireless broadband access system be provided that can provide for SLAs, enabling service providers to have more opportunities for service differentiation and profitability.

5. Class of Service and Quality of Service

In order to implement a practical QoS mechanism, it is desired that a system be able to differentiate between types of traffic or service types so that differing levels of system resources can be allocated to these types. It is customary to speak of "classes of service" as a means of grouping traffic types that can receive similar treatment or allocation of system and media resources.

Currently, there are several methods that can be used in wireline network devices to implement differentiated service classes. Example methods include traffic shaping, admission control, IP precedence, and differential congestion management. It is desired that an IP-centric wireless broadband access system use all of these methods to differentiate traffic into classes of service, to map these classes of service against a QoS matrix, and thereby to simplify the operation and administration of the QoS mechanism.

B. QoS and IP-Centric Wireless Environment

In a point-to-multipoint (PtMP) wireless system like the present invention, it is desirable that the QoS mechanism cope not only with wireline networking considerations, but also with considerations particular to the wireless environment. As stated earlier, it is desired that the inherent BER of wireless be handled. The high BER can require that error detection, correction, and re-transmission be done in an efficient manner. It is desired that a BER handling mechanism also work efficiently with the re-transmission algorithms of TCP/IP so as to not cause further unnecessary degradation of bandwidth utilization. An additional challenge of wireless is contention among users for limited wireless bandwidth. It is desirable that the system handle service requests from multiple users in a radio medium subject to interference and noise, which can make efficient allocation of radio bandwidth difficult.

As discussed above, the change from circuit-switched and ATM data networks to packet-switched data networks has impacted the definition of QoS mechanisms. The present invention provides a novel QoS mechanism in a point-to-multi-point IP-centric wireless system for packet-switched network traffic. In order for the system to provide optimal QoS performance, it desirable that it include a novel approach to QoS mechanisms. The use of QoS as the underlying guide to system architecture and design constitutes an important, substantial and advantageous difference of the IP-centric wireless broadband access system of the present invention over existing wireless broadband access systems designed with traditional circuit-centric or ATM cell circuit-centric approaches such as those used by Teligent and Winstar.

C. IP-Centric Wireless Broadband Access QoS and Queuing Disciplines

1. Managing Queues

Queuing is a commonly accepted tool required for manipulating data communications flows. In order for packet headers to be examined or modified, for routing decisions to made, or for data flows to be output on appropriate ports, it is desirable that data packets be queued. However, queuing introduces, by definition, a delay in the traffic streams that can be detrimental, and can even totally defeat the intent of queuing. Excessive queuing can have detrimental effects on traffic by delaying time sensitive packets beyond their useful time frames, or by increasing the RTT (Round Trip Time), producing unacceptable jitter or even causing the time-out of data transport mechanisms. Therefore, it is desired that queuing be used intelligently and sparingly, without introducing undue delay in delay-sensitive traffic such as real-time sessions.

In a wireless environment where time division multiple access (TDMA), forward error detection (FEC), and other such techniques can be necessary, it is desirable that queuing be used merely to enable packet and radio frame processing. However, in the case of real-time flows, the overall added delay in real-time traffic can preferably be held to below approximately 20 milliseconds.

The use of queue management as the primary QoS mechanism in providing QoS-based differentiated services is a simple and straight forward method for wireless broadband systems. However, wireless systems are usually more bandwidth constrained and therefore more sensitive to delay than their wireline counterparts. For this reason, it is desirable that QoS-based differentiated services be provided with mechanisms that go beyond what simple queuing can do. However, some queuing can still be required, and the different queuing methods are now discussed.

2. First in, First out (FIFO) Queuing

First in, first out (FIFO) queuing can be used in wireless systems, like wireline systems, in buffering data packets when the downstream data channel becomes temporarily congested. If temporary congestion is caused by bursty traffic, a FIFO queue of reasonable depth can be used to smooth the flow of data into the congested communications segment. However, if the congestion becomes severe in extent, or relatively long in duration, FIFO can lead to the discarding of packets as the FIFO queues are filled to capacity and the network is not capable of accepting additional packets causing discarding of packets, i.e. so-called "packet-tossing." Although this can have a detrimental effect on QoS in and of itself, the discarding of packets may cause future problems with traffic flow as the TCP protocol causes the retransmission of lost packets in the proper sequence, further exacerbating the problem. The problem of packet discards can be minimized by increasing the size of the FIFO buffers so that more time can pass before discards occur. Unfortunately, eventually the FIFO can become large enough that packets can become too old and the round-trip time (RTT) can increase to the point that the packets are useless, and the data connection is virtually lost.

In a wireless broadband environment, the requirement for FIFO queuing is partially dependent upon the type of RF access method being used. For time division multiple access/time division duplex (TDMA/TDD), it can be desirable that data be queued even for collecting enough data for the construction of data frames for transmission. Frequency division multiple access (FDMA) and code-division multiple access (CDMA) are not as "sequential" in nature as TDMA, and therefore have less of a requirement for FIFO queuing. However, generally for all wireless access techniques, noise and interference are factors that can lead to retransmissions, and therefore further delays and consequent adverse effect on QoS.

Using FIFO queuing, shared wireless broadband systems can uniformly delay all traffic. This can seem to be the "fairest" method, but it is not necessarily the best method if the goal is to provide high QoS to users. By using different types of queue management, a much better base of overall QoS can be achieved.

3. Priority Queuing

The shared wireless broadband environment can include a constricted bandwidth segment as data is transmitted over the RF medium. Therefore, regardless of access technique, these systems can require some amount of queuing. However, using FIFO queuing can result in a constant delay to all traffic, regardless of the priority or type of traffic. Most data communications environments can consist of a mixture of traffic, with combinations of real time interactive data, file and data downloads, web page access, etc. Some of these types of traffic are more sensitive to delay, and jitter, than others. Priority queuing simply reorders data packets in the queue based on their relative priorities and types, so that data from more latency- and jitter-sensitive traffic can be moved to the front of the queue.

Unfortunately, if there is downlink data channel congestion, or congestion caused by an overabundance of high priority traffic, the condition of "buffer starvation" can occur. Because of the relative volume of high priority packets consuming a majority of buffer space, little room is left for lower priority packets. These lower priority packets can experience significant delays while system resources are devoted to the high priority packets. In addition to low priority packets being held in buffers for long periods of time, or never reaching the buffers, resulting in significantly delayed data flows for these packets, the actual applications corresponding to these low priority packets can also be disrupted, and stop working. Because of the nature of this queuing approach, overall latency and jitter and RTT for lower priority packets can be unpredictable, having an adverse effect on QoS.

If queue sizes are small, reordering data within the queues can have little beneficial effect on the QoS. In fact, processing required to examine packet headers in order to obtain the information necessary to reorder the queues may itself add significant delay to the data stream. Therefore, particularly for wireless broadband data environments, priority queuing can be not much better than FIFO queuing as a QoS mechanism.

4. Classed Based Queuing

By allocating queue space and system resources to packets based on the class of the packets, buffer starvation can be avoided. Each class can be defined to include of data flows with certain similar priorities and types. All classes can be given a certain minimum level of service so that one high priority data flow cannot monopolize all system resources. With the classification approach, because no data flow is ever completely shut off, the source application can receive information about the traffic rate, and can be able to provide TCP-mediated transmission rate adjustment supporting smooth traffic flow.

Although this approach can work better than FIFO queuing in wireless broadband systems, latency and jitter sensitive flows can still be adversely affected by high priority flows of large volume.

5. Weighted Fair Queuing

A weighted fair queuing method can attempt to provide low-volume flows with guaranteed queuing resources, and can then allow remaining flows, regardless of volume or priority, to have equal amounts of resource. Although this can prevent buffer starvation, and can lead to somewhat better latency and jitter performance, it can be difficult to attain stable performance in the face of rapidly changing RF downlink channel bandwidth availability.

Providing a high quality of service can require a QoS mechanism that is more sophisticated than simple queue management.

D. IP-Centric Wireless Broadband Access QoS and TCP/IP

1. TCP/IP

The TCP/IP protocol stack has become the standard method of transmitting data over the Internet, and increasingly it is becoming a standard in virtual private networks (VPNs). The TCP/IP protocol stack includes not only internet protocol (IP), but also transmission control protocol (TCP), user datagram protocol (UDP), and internet control message protocol (ICMP). By assuming that the TCP/IP protocol stack is the standard network protocol for data communications, the creation of a set of optimal QoS mechanisms for the wireless broadband data environment is more manageable. QoS mechanisms can be created that can span the entire extent of the network, including both the wireline and the wireless portions of the network. These mechanisms can integrate in a smooth and transparent manner with TCP rate control mechanisms and provide end-to-end QoS mechanisms that are adaptive to both the wireline and wireless portions of the network. Of course, segments of the wireline network that are congested or are experiencing other transport problems cannot be solved by a wireless QoS mechanism. However, a wireless QoS mechanism can optimize data flows in a manner that can enhance the end user experience when there is no severe wireline network congestion or bottleneck present.

2. Differentiation by Class

Data traffic can be handled based on classes of service, as discussed above. To differentiate traffic by class, data traffic (or a sequence of data packets associated with a particular application, function, or purpose) can be classified into one of several classes of service. Differentiation can be done on the basis of some identifiable information contained in packet headers. One method can include analyzing several items in, e.g., an IP packet header, which can serve to uniquely identify and associate the packet and other packets from that packet flow with a particular application, function or purpose. As a minimum, a source IP address, a source TCP or UDP port, a destination IP address, and a destination IP or UDP port can serve to associate packets into a common flow, i.e. can be used to classify the packets into a class of service.

By creating a finite and manageable number of discrete classes of service, multiple IP flows can be consolidated and handled with a given set of QoS parameters by the QoS mechanisms. These classes can be defined to provide common and useful characteristics for optimal management in the combined wireline and wireless network segments.

3. Per-Flow Differentiation

A finite and discrete set of classes of service, can enable QoS mechanisms to be less compute-intensive, to use less memory, fewer state machines, and therefore have better scaleability than having individual QoS mechanisms (or sets of parameters) for each individual IP flow. However, in a network access device such as, e.g., a point to multi-point (PtMP) wireless broadband access system, the total number of simultaneous IP flows typically will not exceed the range of 1000, and therefore the amount of processing overhead that could be required could permit a per-flow QoS differentiation without resorting to classes of service. However, class of service consolidation of IP flows provides advantages related to marketing, billing and administration.

Prior to the present invention, per-flow differentiation has not been used in a wireless environment (including radio frequencies transmitted over coaxial cables and satellite communications).

4. Using IP Precedence for Class of Service

IP precedence bits in a type of service (IP TOS) field, as described in Internet Engineering Task Force (IETF)1992b, can theoretically be used as a means to sort IP flows into classes of service. IETF RFC1349 proposed a set of 4-bit definitions with 5 different meanings: minimize delay; maximize throughput; maximize reliability; minimize monetary cost; and normal service.

These definitions could add significantly to networks, routers and access devices in differentiating different types of flow so that resources could be appropriately allocated, resulting in improved QoS. However, the proposal has not been widely used. Several proposals in the IETF could make use of this field, along with resource reservation protocol (RSVP), to improve network handling of packets.

Although the type of service (TOS) field has been an integral component of the TCP/IP specification for many years, the field is not commonly used. Absent appropriate bits in the field being set by a source processor, the access devices, the network and network routers cannot implement QoS mechanisms.

5. TCP-Mediated Transmission Rate Mechanisms

The manner in which TCP governs transmission rate can be incorporated and managed by an IP-centric wireless QoS mechanism. If a TCP mechanism is not managed, any wireless QoS mechanism can be overwhelmed or countered by wireless bandwidth factors. Before addressing the specific wireless factors that can impact TCP transmission speed, a review of TCP transmission rate mechanism is needed.

TCP can control transmission rate by "sensing" when packet loss occurs. Because TCP/IP was created primarily for wireline environment with its extremely low inherent BER, such as those found over fiber optic lines, any packet loss is assumed by TCP to be due to network congestion, not loss through bit error. Therefore, TCP assumes that the transmission rate exceeded the capacity of the network, and responds by slowing the rate of transmission. However, packet loss in the wireless link segment is due primarily to inherently high BER, not congestion. The difference turns out to be not insubstantial.

TCP can initially cause the transmission rate to ramp-up at the beginning of a packet flow, and is called slow-start mode. The rate can be continuously increased until there is a loss or time-out of the packet-receipt acknowledgment message. TCP can then "back-off", can decrease the transmission window size, and then can retransmit lost packets in the proper order at a significantly slower rate. TCP can then slowly increase the transmission rate in a linear fashion, which can be called congestion-avoidance mode.

If multiple users share a wireless radio link as with the present invention, the inherently high BER of the medium could potentially cause frequent packet loss leading to unproductive TCP retransmission in congestion avoidance mode. Because wireless bandwidth can be a precious commodity, a IP-centric wireless QoS mechanism preferably provides for packet retransmission without invoking TCP retransmission and consequent and unnecessary "whipsawing" of the transmission rate. This, along with several other factors, makes desirable creation of an IP-centric wireless media access control (MAC) layer. One function of an IP-centric MAC layer can be to mediate local retransmission of lost packets without signaling TCP and unnecessarily altering the TCP transmission speed. A primary task of the IP-centric wireless MAC layer is to provide for shared access to the wireless medium in an orderly and efficient manner. The MAC layer according to the present invention, Proactive Reservation-based Intelligent Multimedia-aware Media Access (PRIMMA) layer, available from Malibu Networks Inc., of Calabasas, Calif., can also schedule all packet transmissions across the wireless medium on the basis of, e.g., IP flow type, service level agreements (SLAs), and QoS considerations.

6. TCP Congestion Avoidance in an IP-Centric Wireless System

a. Network Congestion Collapse, Global Synchronization and IP-Centric Wireless TCP Congestion Avoidance

The inherently high bit error rate (BER) of wireless transmission can make an occurrence of problems known as congestion collapse or global synchronization collapse more likely than in a wireline environment. When multiple TCP senders simultaneously detect congestion because of packet loss, the TCP senders can all go into TCP slow start mode by shrinking their transmission window sizes and by pausing momentarily. The multiple senders can then all attempt to retransmit the lost packets simultaneously. Because they can all start transmitting again in rough synchrony, a possibility of creating congestion can arise, and the cycle can start all over again.

In the wireless environment, an occurrence of burst noise can cause packet loss from many IP streams simultaneously. The TCP transmission rate mechanisms of the TCP senders can assume that packet loss was due to congestion, and they can all back-off in synchrony. When the TCP senders restart, the senders can restart in rough synchrony, and indeed can now create real congestion in the wireless link segment. This cyclical behavior can continue for some time, and can possibly cause unpredictable system performance. This can be due in part to overflowing system queues which can cause more packets to be dropped and can cause more unproductive retransmissions. This can degenerate into a "race" state that could take many minutes before re-establishing stability; this can have an obvious negative impact on QoS.

In the wireline world, random early detection (RED) can be used to circumvent global synchronization. By randomly selecting packets from randomly selected packet flows before congestion collapse occurs, global synchronization can be avoided. Queues can be monitored, and when queue depth exceeds a preset limit, RED can be activated, activating asynchronously the TCP senders' transmission rate controllers. This can avoid the initial congestion which would otherwise result in collapse and then global synchronization.

Instead of purely random packet discards, the packets to be discarded can be done with consideration to packet priority or type. While still random, the probability of discard for a given flow can be a function of the by packet priority or type. In a wireless system, weighted random early detection (WRED) can be used without the concern of retransmission and TCP rate reset by preferentially selecting UDP packets of real time IP flows such as streaming audio, and H.323 flows with a more critical packet Time-to-Live parameter. These IP flows are more sensitive to latency and jitter, and less sensitive to packet loss.

In the wireless environment, with an appropriately designed MAC layer, packet loss due to BER that might otherwise trigger congestion collapse and global synchronization can best be managed with local retransmission of lost packets according to the present invention and without RED and the unnecessary retransmission of packets by the TCP sender and the resulting reset of TCP transmission rate. The IP-centric wireless system separately manages the TCP transmission window of the TCP sender remotely by transmitting a packet receipt-acknowledgment before the TCP sender detects a lost packet and initiates retransmission along with an unnecessary reset of the transmission rate. This IP-centric wireless system TCP transmission window manager communicates with the MAC layer in order to be aware of the status of all packets transmitted over the wireless medium.

b. The Effect of Fractal Self-Similar Network Traffic Characteristics vs. Poisson Distributions on Network Congestion

Conventionally, it has been believed that network traffic can be modeled with a Poisson distribution. Using this distribution leads to the conclusion, through system simulations, that the sum of thousands of individual traffic flows with Poisson distributions results in a uniform overall network traffic distribution. In other words, the overall network can "average-out" the burstiness of individual traffic flows. Using this model, network congestion behavior, burst behavior, and dynamic traffic characteristics have been used to create conventional congestion avoidance strategies, design queue buffer sizes in network devices, and traffic and capacity limitation predictions.

More recent studies have demonstrated that TCP/IP-based traffic causes networks to behave in a fractal, or self-similar fashion. With this model, when the burstiness of individual traffic flows is summed for the entire network, the entire network becomes bursty. The bursty nature of network traffic flow is seen over all time scales and flow scales of the network. This has huge implications both in design of an IP-centric wireless broadband system according to the present invention, and in the design of congestion avoidance strategies in the network as a whole. With this new perspective on network behavior, it has become clear that network routers, switches and transmission facilities in many cases have been "under-engineered." This under-engineering has led to a further exacerbation of the congestion behavior of the network.

The implications for IP-centric wireless system architecture and design range from queue buffer capacity to local congestion avoidance strategies. Because wireless systems have the added burden of a high inherent BER, the effect of network-wide congestion behavior on local (wireless media channel) congestion avoidance strategies must be properly gauged and countered. For this reason, it is desirable that congestion avoidance algorithms of the IP-centric wireless system be crafted to optimize traffic flow with new mathematical and engineering considerations that until very recently were not apparent or available to system designers.

With these considerations in mind, IP-centric wireless system design cannot be done with the conventional wireline system design approaches without resulting in very low system performance characteristics. With traditional design approaches of a circuit-centric wireless system, bandwidth utilization, real time multimedia quality, and overall system QoS provide for a dramatically lower end-user experience.

7. Application-Specific Flow Control in an IP-Centric Wireless System

With a range of data flows, each having different bandwidth, latency and jitter requirements, for the achievement of high QoS as perceived by the end user, it is desirable that the IP-centric wireless system be able to manage QoS mechanism parameters over a wide range, and in real time. The QoS mechanism must be able to alter system behavior to the extent that one or more data flows corresponding to specific applications be switched on and off from appropriate end users in a transparent manner. This approach is in contrast to other QoS mechanisms that seek to achieve high QoS by establishing circuit-centric connections from end to end without regard for an underlying application's actual QoS requirements. By using the present invention, providing a QoS mechanism that is application-specific rather than circuit-specific, scarce wireless bandwidth can be conserved and dynamically allocated where needed by the QoS mechanisms associated with each application type.

B. QoS and IP-Centric Wireless Media Access Control

1. Proactive Reservation-based Intelligent Multimedia-aware Media Access (PRIMMA) MAC Layer

The present invention's proactive reservation-based intelligent multimedia-aware media access (PRIMMA) media access control (MAC) layer provides an application switching function of the IP-centric wireless QoS mechanism. Once the nature and QoS requirements of each IP stream are determined by other portions of the system, this information is communicated to the PRIMMA MAC layer so that the IP flows of each application can be switched to appropriate destinations in a proper priority order.

2. PRIMMA IP Protocol Stack Vertical Signaling

For IP streams that originate from a local user's CPE, application-level information about the nature of the application can be used by the system to assign appropriate QoS mechanism parameters to the IP stream. For IP streams that originate from a non-local host, information about the IP streams for use in configuring the appropriate QoS mechanism parameters can be extracted from packet headers. The information about the IP streams is communicated "vertically" in the protocol stack model from the application layer (i.e. OSI level 7) to the PRIMMA MAC layer (i.e. OSI level 2) for bandwidth reservation and application switching purposes. Although this violates the conventional practice of providing isolation and independence to each layer of the protocol stack, thereby somewhat limiting the degree of interchangeability for individual layers of the stack, the advantages far outweigh the negatives in an IP-centric wireless broadband access system.

3. PRIMMA IP Flow Control and Application Switching

Based on a specific set of QoS requirements of each IP application flow in the IP-centric wireless system, applications are switched in a "proactive" manner by appropriate reservations of bandwidth over the wireless medium. The wireless transmission frames in each direction are constructed in a manner dictated by the individual QoS requirements of each IP flow. By using QoS requirements to build the wireless transmission frames, optimal QoS performance can result over the entire range of applications being handled by the system. For example, latency and jitter sensitive IP telephony, other H.323 compliant IP streams, and real-time audio and video streams can be given a higher priority for optimal placement in the wireless transmission frames. On the other hand, hypertext transport protocol (HTTP) traffic, such as, e.g., initial web page transmissions, can be given higher bandwidth reservation priorities for that particular application task. Other traffic without latency, jitter, or bandwidth requirements such as, e.g., file transfer protocol (FTP) file downloads, email transmissions, can be assigned a lower priority for system resources and placement in the wireless transmission frame.

4. PRIMMA TCP Transmission Rate Agent

Wireless end users are separated from a high speed, low BER wireline backbone by a lower speed, high BER wireless segment which can be subject to burst error events. TCP/IP traffic that traverses the wireless segment can experience frequent packet loss that, without intervention, can create congestion collapse and global synchronization as previously discussed. Therefore, it is desirable that the present invention's IP-centric wireless system make use of a TCP transmission rate agent that can monitor packet loss over the wireless segment, and can manage the remote TCP transmission rate function by recreating and transmitting any lost packet acknowledgments. The PRIMMA MAC layer can itself retransmit any lost packets over the wireless medium.

The IP-centric wireless TCP transmission rate agent or "adjunct" can also flow-control the IP streams when necessary, and in accordance with the QoS requirements of the IP flows. All IP-centric wireless TCP transmission rate agent functionality can be transparent to both local and remote hosts and applications.

F. Telecommunications Networks

1. Voice Network

a. Simple Voice Network

FIG. 1A is a block diagram providing an overview of a standard telecommunications network 100 providing local exchange carrier (LEC) services within one or more local access and transport areas (LATAs). Telecommunications network 100 can provide a switched voice connection from a calling party 102 to a called party 110. FIG. 1A is shown to also include a private branch exchange 112 which can provide multiple users access to LEC services by, e.g., a private line. Calling party 102 and called party 110 can be ordinary telephone equipment, key telephone systems, a private branch exchange (PBX) 112, or applications running on a host computer. Network 100 can be used for modem access as a data connection from calling party 102 to, for example, an Internet service provider (ISP) (not shown). Network 100 can also be used for access to, e.g., a private data network. For example, calling party 102 can be an employee working on a notebook computer at a remote location who is accessing his employer's private data network through, for example, a dial-up modem connection.

FIG. 1A includes end offices (EOs) 104 and 108. EO 104 is called an ingress EO because it provides a connection from calling party 102 to public switched telephone network (PSTN) facilities. EO 108 is called an egress EO because it provides a connection from the PSTN facilities to a called party 110. In addition to ingress EO 104 and egress EO 108, the PSTN facilities associated with telecommunications network 100 include an access tandem (AT) (not shown) at points of presence (POPs) 132 and
134 that can provide access to, e.g., one or more inter-exchange carriers (IXCs) 106 for long distance traffic, see FIG. 2A. Alternatively, it would be apparent to a person having ordinary skill in the art that IXC 106 could also be, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral (IP).

FIG. 1A also includes a private branch exchange (PBX) 112 coupled to EO 104. PBX 112 couples calling parties 124 and 126, fax 116, client computer 118 and associated modem 130, and local area network 128 having client computer 120 and server computer 122 coupled via an associated modem 130. PBX 112 is a specific example of a general class of telecommunications devices located at a subscriber site, commonly referred to as customer premises equipment (CPE).

Network 100 also includes a common channel interactive signaling (CCIS) network for call setup and call tear down. Specifically, FIG. 1 includes a Signaling System 7 (SS7) signaling network 114. Signaling network 114 will be described further below with reference to FIG. 2B.

b. Detailed Voice Network

FIG. 2A is a block diagram illustrating an overview of a standard telecommunications network 200, providing both LEC and IXC carrier services between subscribers located in different LATAs. Telecommunications network 200 is a more detailed version of telecommunications network 100. Calling party 102a and called party 110a are coupled to EO switches 104a and 108a, respectively. In other words, calling party 102a is homed to ingress EO 104a in a first LATA, whereas called party 110a is homed to an egress EO 108a in a second LATA. Calls between subscribers in different LATAs are long distance calls that are typically routed to IXCs. Sample IXCs in the United States include AT&T, MCI and Sprint.

Telecommunications network 200 includes access tandems (AT) 206 and 208. AT 206 provides connection to points of presence (POPs) 132a, 132b, 132c and 132d. IXCs 106a, 106b and 106c provide connection between POPs 132a, 132b and 132c (in the first LATA) and POPs 134a, 134b and 134c (in the second LATA). Competitive local exchange carrier (CLEC) 214 provides an alternative connection between POP 132d and POP 134d. POPs 134a, 134b, 134c and 134d, in turn, are connected to AT 208, which provides connection to egress EO 108a. Called party 110a can receive calls from EO 108a, which is its homed EO.

Alternatively, it would be apparent to a person having ordinary skill in the art that an AT 206 can also be, for example, a CLEC, or other enhanced service provider (ESP), an international gateway or global point-of-presence (GPOP), or an intelligent peripheral.

Network 200 also includes calling party 102c homed to CLEC switch 104c. Following the 1996 Telecommunications Act in the U.S., CLECs gained permission to compete for access within the local RBOCs territory. RBOCs are now referred to as incumbent local exchange carriers (ILECs).

i. Fixed Wireless CLECs

Network 200 further includes a fixed wireless CLEC 209. Example fixed wireless CLECs are Teligent Inc., of Vienna, Va., WinStar Communications Inc., Advanced Radio Telecom Corp. And the BizTel unit of Teleport Communications Group Inc. Fixed wireless CLEC 20