Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1998-07-24
2003-02-11
Yao, Kwang Bin (Department: 2664)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S395310, C370S401000, C455S433000
Reexamination Certificate
active
06519248
ABSTRACT:
BACKGROUND
This invention relates to construction and control of communication networks that carry packetized data, e.g., Internet-protocol-based (IP-based) traffic, and in particular to network architectures that have large freedom in network topology and simplified network extensions with a lightweight but robust protocol. Applicant's invention is applicable to wired and wireless networks handling packet data traffic, including cellular radio networks handling voice traffic.
It is generally expected that the importance of packet data networks, and in particular IP-based networks, will continue growing. Although a large proportion of current IP-based traffic is “best effort”, in the sense that the network does not guarantee any minimum level of bandwidth or quality of service to a user, the proportion requiring some guaranteed level of quality will only increase in the future. Such guarantees may eventually be provided by the currently evolving differentiated services concept, which is described in D. Clark and J. Wroclawski, “An Approach to Service Allocation in the Internet”, http://ietf.org/internet-drafts/draft-clark-diff-svc-alloc-00.txt, Internet Engineering Task Force (July 1997); K. Nichols, V. Jacobson, and L. Zhang, “A Two-Bit Differentiated Services Architecture for the Internet”, http://ietf.org/internet-drafts/draft-nichols-diff-svc-arch-00.txt, Internet Engineering Task Force (November 1997); and D. Clark and W. Fang, “Explicit Allocation of Best Effort Packet Delivery Service”, http://diffserv.lcs.mit.edu/Papers/exp-alloc-ddc-wf.pdf (November 1997). The demand to access IP-based and other packet data networks from wireless terminals such as those operating in current cellular radio telephone networks will also increase.
Packet data networks are designed and based on industry-wide data standards such as the open system interface (OSI) model or the transmission control protocol/Internet protocol (TCP/IP) stack. In the communications industry, Layer 1 may be called the physical layer, and the Layer 1 protocol defines the parameters of the physical communications channel, e.g., frequency spacing of a radio carrier, modulation characteristics, etc. Layer 2 is called the data link, or hardware interface, layer, and the Layer 2 protocol defines the techniques necessary for the accurate transmission of information within the constraints of the physical channel, e.g., error correction and detection, etc. Layer 3 may be called the network, or resource control, layer, and the Layer 3 protocol defines the procedures for reception and processing of information transmitted over the physical channel. The functionality of a Layer 2 protocol includes the delimiting, or framing, of Layer 3 messages sent between communicating Layer 3 peer entities. In cellular radio telephone systems, an air interface protocol, such as TIA/EIA/IS-136 and TIA/EIA/IS-95 published by the Telecommunications Industry Association and Electronic Industries Association, is a combined Layer 1, 2, and 3 protocol that specifies how remote stations like cellular telephones communicate with base stations and a mobile services switching center (MSC).
These standards have been developed, whether formally or de facto, for many years, and the applications that use these protocols are readily available. The main objective of standards-based networks is to achieve interconnectivity with other networks. The Internet is today's most obvious example of such a standards-based network in pursuit of this goal. One approach to packet-based wireless communication is cellular digital packet data (CDPD), aspects of which are described in U.S. Pat. No. 5,729,531 and U.S. Pat. No. 5,768,267, both to Raith et al., and U.S. Pat. No. 5,751,731 and U.S. Pat. No. 5,757,813, both to Raith; in allowed U.S. patent applications Ser. Nos. 08/544,492 and 08/544,589, both by Raith et al., and Ser. Nos. 08/544,837 through Ser. No. 08/544,839; and in U.S. patent applications Ser. Nos. 08/544,493 and Ser. No. 08/544,835, both by Raith, Ser. No. 08/544,836 by Bilsstrom et al., and Ser. Nos. 08/544,841 and Ser. No. 544,843, both by Raith et al. These patents, allowed applications, and applications are expressly incorporated here by reference.
The bottleneck of IP-based communication with a wireless terminal is the air interface, which may be shared among wireless terminals by using a random access protocol, possibly with some soft-state-based priority for continuous transmissions, or by using a protocol as in conventional cellular radiotelephony that allocates a wireless channel to a terminal on a first-come-first-served basis. For packet data traffic like IP-based traffic, a random access (connection-less) protocol may be more appropriate than a channel allocation (connection-oriented) protocol. Such IP-based information flows originated or terminated by a wireless terminal typically have lower bit rates than the average wired IP flow. This limitation is especially felt when a base station's service area is large because the air interface capacity decreases with increasing cell size, as described in D. F. Bjornland et al., “UMTS—The Universal Mobile Telecommunications System”,
Telektronikk
(August 1996);
IEEE Personal Communication
vol. 4, no. 4 (August 1997); and E. Nikula et al., “FRAMES Multiple Access for UMTS and IMT-2000
”, IEEE Personal Communications
vol. 5, no. 2 (April 1998).
Wireless users may be willing to accept lower bit rates than wired users due to the air interface bottleneck, but wireless users will expect to use the same hardware and software as wired users. Thus, the wired part of the network should be unaware of the mobility of the users, except possibly for minor modifications. Although these features are not strict requirements, a communication system having these features can be expected to be more widely and easily accepted.
Although it is important, air interface bandwidth efficiency may not be the primary requirement for a cellular access network serving IP-based communication. Applicant believes that low equipment cost, robustness, scalability, low maintenance, and easy system establishment and expansion (growth), which are features typical of IP-based networks, will be more important to cellular network operators. Scalability is a feature that makes an architecture or technique applicable to large and small networks; expansion or extension are the actions necessary for making a network larger (e.g., plug in new nodes, etc.). These features are distinct, and both are desirable.
Another problem with cellular systems is that they must keep track of the movements of the served mobile users so that the users can be found when they have incoming calls/data. Usually the system is divided into a large number of cells, making it inefficient to maintain a central database that knows the exact location of each user's terminal because frequent movements generate a large load of movement-indications sent to this central database. On the other hand, such exact location information is desirable because the more precise the location information is, the faster and less wastefully a remote terminal can be found for an incoming call. Network actions taken when a mobile station has an incoming call and has to be searched for (because its exact location is unknown) is usually called paging. The more exact the location information is, the fewer the cells that must be paged for the mobile, which means less load.
In most cellular systems (e.g., systems operating according the GSM standard), an intermediate solution is used. A central database has some information on the location of each remote terminal, but this information is not exact. The service area of the system is divided into location areas, each of which contains a number of cells. The central location database knows in which location area each remote terminal is, but not in which of the location area's cells it is. When a remote terminal has an incoming call, the terminal is paged in all the cells of the known location area. The optimal point in t
Telefonaktiebolaget LM Ericsson (publ)
Yao Kwang Bin
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