Gregory P. Pollini

A profile-based location strategy and its performance

Future microcellular personal communications systems (PCSs) will be characterized by high user density and high mobility. It is expected that registrations will incur a large amount of the radio link signaling traffic. A profile-based strategy (PBS) is proposed to reduce the signaling traffic on the radio link by increasing the intelligence within the fixed network. The system maintains a sequential list of the most likely places where each user is located. The list is ranked from the most to the least likely place where a user is found. When a call arrives for a mobile, it is paged sequentially in each location within the list. When a user moves between location areas in this list, no location update is required. The list may be provided by the user or may be based on each users past calling history. The method for doing this is outside the scope of this work. This work focuses on the potential performance improvements that can result from maintaining such a list. This paper compares the performance of the proposed strategy to the typical geographic-based location-tracking schemes being implemented in evolving digital cellular and cordless standards. Key performance measures for the comparison are radio bandwidth, fixed network SS7 traffic, and call setup delay. We investigate the conditions under which the PBS performs better than the traditional scheme. Results indicate that over a wide range of parameters, it may be possible to reduce both the radio bandwidth and fixed network signaling load for a modest increase in call setup delay.

Network control for wireless communications

Existing wireless network architectures and the increasing demand for cellular services are reviewed. Wireless network control tasks and the structure of a cellular packet switch (CPS) based on an optical fiber metropolitan area network (MAN) are described. Protocols for moving information through the MAN focusing on handoff, a crucial function of wireless networks, are discussed. The results of an analysis of switch performance as measured by capacity and the distribution of functionality are presented. Several open issues regarding the capability of the CPS to deliver telephone service to wireless terminals, including privacy and security issues, are discussed.<<ETX>>

PCS mobility management using the reverse virtual call setup algorithm

The increased demand for wireless mobile communications coupled with the finite available spectrum has motivated investigation into alternative methods of tracking users and delivering calls. We present a new scheme for delivering mobile terminated calls named reverse virtual call setup (RVC). Only a few new fixed network SS7 signaling messages are needed to implement this protocol; we specify them here. RVC can function within the existing cellular paging network or with an integrated overlaid paging network. The relative performance of RVC for both scenarios is investigated.

Network protocols for the cellular packet switch

Future wireless information networks will employ dense grids of base stations to support a high user population. While small cells mitigate capacity problems, lengthen battery life, and improve signal quality, the frequent movement of users across cell boundaries imposes new burdens on network controllers. Previous work suggests that a cellular packet switch, based on distributed network control, can support high density personal communications. This paper proposes an allocation of control functions to elements of the cellular packet switch and specifies the flow of information within the switch. Message flows, defined for key procedures, form the foundation of a network layer protocol. Functionality is divided into the categories of call processing (set up and release), mobility management (location updates, handover, and path optimization), and radio resource management. Central office switches perform call processing. Mobility management and radio resource management are performed by interface units of the metropolitan area network at the heart of the cellular packet switch. This architecture delivers advanced services with minimal impact on central office switch software. It also relies on distributed, rather than centralized mobility management to provide prompt, accurate communications as users move about. >

The intelligent network signaling and switching costs of an alternate location strategy using memory

In future high density microcellular personal communications systems (PCS), it is expected that most of the signaling traffic will come from registrations. An alternate location strategy has been proposed to reduce the signaling traffic on the radio link by increasing the responsibilities placed upon the fixed network. A fixed network performance comparison to the classic location strategy being implemented in evolving digital cellular and cordless standards is presented. The key measures are SS7 traffic and switching complexity. An example based on the Groupe Speciale Mobile (GSM) system illustrates the results.

Signaling system performance evaluation for personal communications

A key measure of wireless network performance is the amount of signaling information needed to deliver calls to mobile users. Estimates of the signaling system loading are widely available in recent literature. However, in all of the available publications the results are heavily dependent upon assumptions about user density, velocity, cell sizes, and other quantities related to the system and users. This paper presents a methodology to evaluate the signaling system loading that can produce general results that are independent of these assumptions. The technique relies upon the definition of an index of mobility which aggregates several key quantities in a single measure. With this index as the independent variable, graphical results reveal the behavior of a system. This paper evaluates three protocols: GSM Pan-European Cellular, IS-41 North American Cellular, and Bellcores PCS Access Service for Networks. The method is general and can be easily applied to a new system.

Handover protocols between metropolitan area networks

Inter-MAN handover protocols for the cellular packet switch are developed, based on interconnecting MANs via gateways. Inter-MAN handover protocols utilize the gateway to maintain a connection as a user moves across MAN boundaries. This greatly reduces the fixed-network signalling traffic while protecting information in data communications.<<ETX>>

A wireless service for the IEEE 802.6 metropolitan area network

The authors explore how to use specific features in the IEEE 802.6 standard to allow the metropolitan area network to function as a cellular packet switch. They compare the needs of wireless voice, data, and signaling with existing 802.6 capabilities and find that several new features are required. The proposed voice service allows voice packets from the radio link to be carried in a single 802.6 slot of 53 bytes. This is accomplished by eliminating portions of the 802.6 adaptation layer which are unneeded for voice. Signaling traffic is accommodated by use of the virtual circuit identifier and the message identification fields to provide virtual circuits, permanent virtual circuits, and point-to-multipoint virtual circuits. Low bit rate data can be supported using the existing 802.6 connection-oriented service with retransmission at the segmentation and reassembly sublayer.<<ETX>>

Optimum location area sizes and reverse virtual call setup in PCS networks

The increased demand for wireless PCS communications coupled with limited spectrum has motivated many to investigate techniques that minimize the radio link traffic needed to deliver calls to users and to track their locations. As the location area increases, the paging cost increases and the registration cost decreases. Previous work minimized the radio link traffic in a single cell along the perimeter of a location area. In this paper, we minimize the total radio bandwidth traffic throughout the entire system. This approach results in a larger location area. This will reduce the fixed network signaling load. This paper also briefly describes a new scheme for delivering mobile terminated calls called the reverse virtual call setup (RVC) algorithm. We evaluate the radio link cost when a separate overlaid paging system is used in conjunction with RVC. It is shown to be relatively insensitive to location area size over a large range of practical parameters. Results indicate that the location area size should be as large as the restrictions of finite bandwidth and power permit. A one-to-one relationship between a mobile switching center (MSC) and a location area is shown to be a good solution.

Efficient routing of information between interconnected cellular mobile switching centers

At the switch boundaries of cellular systems, it is necessary to provide an inter-switch handover procedure if calls are to remain in progress as users cross these boundaries. Both the North American and Pan European second generation standards provide mechanisms for inter-switch handover. Motivated by the need to develop procedures for inter-switch handover in the cellular packet switch (CPS), this paper develops a general set of procedures for inter-switch handover that, unlike their second generation counterparts, provide a mechanism for the transport of data. Unlike voice, data packets must all be delivered. The delivery may need to be sequential and/or restricted to a single copy. The path optimization procedures are all presented in the context of the CPS. In addition, we identify capabilities needed by the CPS and present suitable protocols. The path optimization procedures are evaluated based on the following performance criteria: guarantee of sequential delivery, avoidance of multiple copies, and delay. Fundamental limitations on data throughput result if both sequential delivery and a single copy are required.