Methods and apparatus for random backoff based access...

Details Methods and apparatus for random backoff based access... Methods and apparatus for random backoff based access...

1998-10-14

2003-07-15

Ton, Dang (Department: 2666)

Multiplex communications

Communication over free space

Having a plurality of contiguous regions served by...

C370S342000

Reexamination Certificate

active

06594240

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to methods and apparatus for providing access priority control in a communications system and, more particularly, to methods and apparatus for providing access priority control in a media access control protocol of a Universal Mobile Telecommunications System.
BACKGROUND OF THE INVENTION
A major effort has been underway in the last decade to integrate multimedia capabilities into mobile communications. The International Telecommunications Union (ITU) and other organizations have been attempting to develop standards and recommendations that ensure that mobile communications of the future will be able to support multimedia applications with at least the same quality as existing fixed networks. Particularly, many global research projects have been sponsored in order to develop such next (third) generation mobile systems. Research and Development of Advanced Communication Technologies in Europe, RACE-1, and RACE-2, and Advanced Communications Technology and Services (ACTS) are examples of such efforts in Europe. It is known that in order to provide end users with the requisite service quality for multimedia communications, Internet access, video/picture transfer, high bit rate capabilities are required. Given such requirements, bearer capability targets for a third generation system have been defined as 384 kilobits per second (kb/s) for full coverage area and 2 Megabits per second (Mb/s) for local area coverage.
Universal Mobile Telecommunications System (UMTS) is a new radio access network based on 5 Megahertz Wideband Code Division Multiple Access (W-CDMA) and optimized for support of third generation services including multimedia-capable mobile communications. Since major design goals of UMTS are to provide a broadband multimedia communications system that integrates infrastructure for mobile and fixed communications and to offer, inter alia, the same range of services as provided by the fixed and wireless communications networks, UMTS must provide circuit-switched as well as packet-switched services, a variety of mixed-media traffic types, and bandwidth-on-demand. However, providing multimedia support implies the need for flexibility, that is, being able to support services with different bit rates and E
b
/N
0
requirements, and to multiplex such services in a multiservice environment. UMTS is designed to be able to support such demands.
Referring to
FIG. 1
, an exemplary block diagram of a UMTS access network is shown. Particularly, a plurality of remote terminals
2
and
4
(e.g., mobile terminals) communicate with base stations (NODE-B)
6
via W-CDMA wireless links
8
. The remote terminals may be a variety of devices such as a wireless phone
2
or a portable personal computer
4
with an internal or external modem. In the UMTS standard, a base station is called a NODE-B. These base stations communicate with a network component that provides radio resource management functions and is called a Radio Network Controller (RNC). Since UMTS is a W-CDMA system, soft handoffs are supported. In the case of soft handoffs, there are two base stations
6
serving one remote terminal. Thus, the remote terminal sends frames to these two base stations. When the two base stations receive the frames from the remote terminal, they send them to a Frame Selector Unit (FSU). The FSU decides which is a better frame, in terms of frame quality, to be sent to the core network. In UMTS, the FSU may be physically integrated with the RNC and as such, in
FIG. 1
, the RNC and FSU are shown as block
10
, but also are separated functionally as block
12
(FSU) and block
14
(RNC). Other elements in the UMTS network perform conventional functions such as: the xLR databases
20
, which provide home and visiting location information; and the interworking function (IWF) units
22
. It is to be appreciated that the Universal Mobile Switching Center (UMSC)
16
serves as the mobile switching center for the base stations
6
in the UMTS. Sub-networks
18
are wireless service provider networks and CN
1
through CNn are the core networks
24
to which the remote terminals are ultimately coupled.
Referring to
FIG. 2
, a diagram of,the typical protocol stack in UMTS is shown. In UMTS, Layer
1
(L
1
) is the physical layer (PHY) which offers information transfer services to the MAC (Media Access Control) layer and higher layers. The physical layer transport services are described by how and with what characteristics data is transferred over the transport channels of the radio interface. Layer
2
(L
2
) is comprised of sublayers which include MAC, LAC (Link Access Control), and RLC and RLC′ (Radio Link Control). In UMTS, the functions performed in RLC are split and thus two RLC protocols (RLC and RLC′) are specified. The RLC and MAC layers provide real-time and non-real-time services. The MAC layer controls but does not carry out the multiplexing of data streams originating from different services. That is, the MAC layer, via logical channels, allows common physical communications channels (e.g., broadcast channel) to be shared by a number of remote terminals. IP (Internet Protocol) is the network layer.
“Uu” refers to the UMTS-specific interface between a remote terminal and a base station, while “Iub” refers to the UMTS-specific interface between a base station and the RNC/FSU. Layer
2
of the radio access network(i.e., left side of NODE-B on the protocol stack) is split into RLC and MAC layers, while Layer
2
of the core network (i.e., right side of NODE-B on the protocol stack) is more related to the technology used to transport network layer frames, e.g., ATM (Asynchronous Transfer Mode) or Frame Relay. IP is shown as the transport protocol, however, UMTS is not so limited. That is, UMTS can cater to other transport protocols. Further details on the protocol layers may be found in Dahlman et al., “UMTS/IMT-2000 Based on Wideband CDMA,” IEEE Communications Magazine, pp. 70-80 (September 1998) and in ETSI SMG2/UMTS L2 & L3 Expert Group, “MS-UTRAN Radio Interface Protocol Architecture; Stage 2,” Tdoc SMG2 UMTS-L23 172/98 (September 1998).
In UMTS, four types of application traffic need to be handled. They include: (i) applications that are both delay and loss sensitive, e.g., interactive video; (ii) applications that are loss sensitive but can tolerate moderate delay, e.g., interactive data; (iii) applications that are delay sensitive but tolerant of moderate losses, e.g., voice; and (iv) applications that are tolerant of both delay and losses, e.g., file transfer.
To provide different Quality of Service (QoS) to all these different applications, the UMTS system must be designed appropriately. Several important issues need to be considered in UMTS system design such as, for example, how to satisfy QoS without wasting network resources and how to operate the systems in the stable region when all traffic types burst simultaneously.
Further, several components are required in UMTS to support varying QoS. For example, service parameters need to be defined to enable different applications to specify their different QoS requirements, e.g., the Guaranteed Service and Controlled Load Service. parameters defined by the Internet Engineering Task Force (IETF). Users can ask for bandwidth resources either on a burst mode or connection mode. Also, there must be an admission control component in UMTS that makes decisions as to whether or not users' requests will be granted. The admission of new requests must be done such that even when all admitted requests peak simultaneously, the QoS requirements of each request will not be violated (unless they are best-effort requests). Further, once the users' requests are admitted, there must be features implemented in the UMTS network to deliver such service guarantees, e.g., delay requirement, packet loss requirement. Scheduling algorithms at the network nodes and packet marking for non-conformant users' traffic are some of the features that can be supported by routers to provide differentiated

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