Volume 21, 2002, No. 2

A Framework for QoS Support in the UMTS/GPRS Backbone Network Using DiffServ

Farshid AGHAREBPARAST, Victor C. M. LEUNG   Abstract A distinguishing feature of the Universal Mobile Telecommunications System (UMTS) is the support of different levels of quality of service (QoS) as required by subscribers and their applications. To provide QoS, the UMTS backbone network needs an efficient QoS mechanism to provide the demanded level of services on a UMTS core network. This paper presents a methodology of provisioning QoS in this backbone network based on the Differentiated Services (DiffServ) model. DiffServ is a relatively simple but scalable IP-based technology, which can efficiently provide QoS in networks of DiffServ supporting routers. This is accomplished by defining a framework for setting a DiffServ-based UMTS backbone router, as well as the requisite mapping function for interworking between a DiffServ domain and UMTS. Efficient schemes are presented for the scheduling and buffer management components of the backbone router supporting DiffServ. The performance of this system for provisioning UMTS primary QoS classes is evaluated by computer simulations. The results show that DiffServ can be an effective candidate for UMTS backbone bearer service.

 

An Overview of Channel Assignment Schemes for Mobile Cellular Networks

Gary H. K. MA, Albert Y. ZOMAYA   Abstract For many years, telecommunication specialists are working on ways to improve service capacity of cellular networks. Since the radio frequency spectrum allocated for cellular network is limited, it is important to manage this scarce resource carefully in order to meet the ever-growing demand. This paper reviews channel assignment schemes for mobile cellular network. The paper provides a survey of a large number of channel assignment strategies that have been proposed by many researchers over the years. These channel assignment strategies are categorised into four groups. The characteristics and methods for evaluating these channel assignment schemes are also presented.

 

H3M --- A Network Access Methodology Supporting QoS

E. C. FOUDRIAT, K. MALY, Y. LI   Abstract This paper presents a physical and media access layer methodology that is able to significantly improve quality of service (QoS) performance. Since QoS relates to a wide range of features, access protocols supporting it must be multifaceted. This paper presents the H3M (Heterogeneous, Hierarchical, Highly Mobile) network system which supports QOS. First, H3M uses an improved access paradign --- DMNA (Dynamic Multiple Node Access), i.e., nodes decide the manner in which they submit data during their access period. Multiple implies both many nodes interacting and each node submitting all its pending information. Multiple also implies that during an access frame, different access mechanisms are provided for both synchronous and asynchronous message-traffic types. Using DMNA, dynamic recovery of unneeded capacity is made possible and recovered capacity is made available to other nodes and subframes immediately. For example, a voice call in silent phase immediately adjusts to its capacity needs without signaling. This provides an improved level of QoS support over single access, fixed-frame, fixed-slot size technology. H3M access was originally targeted to WLAN (Wireless Local Area Networks); it provides mechanisms for multiple clustering. Intra-clustering uses techniques where all nodes share a band; inter-clustering where clusters are able to communicate across the whole network by using the heterogeneous characteristics that nodes will have differing equipment. Communication across the network is enabled with minimal routing, with predictable delays, with simple multicasting, etc., features which greatly enhance the QoS in H3M. H3M features variable frequency, variable bandwidth (VFVB) channeling base upon Digital Software Radio technology. It enables each cluster to adapt its capacity needs to its present loading. The combination of DMNA to dynamically share bandwidth within a frame and VFVB sharing between frames provides support for load balancing to minimize congestion problems again supporting superior QoS. H3M was originally [17--19] proposed and is still applicable for wired ad hoc local (LAN) and metropolitan (MAN) area networks. Hence, it is able to support Enterprise Networks (EPN), i.e., private shared link networks used by companies, universities, etc., presently using IEEE 802.X technology. With modification, it is applicable to point-to-multipoint networks such as ground-satellite links and mobile telephony. Further, because of H3M versatile nature, it can operate as a bridge-type network with minimal adjustment to packets transferred through and into for bridging between interfaces networks using standard ATM and IEEE protocols. The paper documents H3M performance by simulation at the cluster level. It supports loads ranging up to 80% of capacity and wide variation between synchronous and asynchronous traffic. Synchronous traffic performance is constant throughout the load range; asynchronous traffic shares the remaining effective bandwidth for both large and small message sizes is with no evidence of choking.

 

Depth First Search and Location Based Localized Routing and QoS Routing in Wireless Networks

Ivan STOJMENOVIC, Mark RUSSELL, Bosko VUKOJEVIC   Abstract In a localized routing algorithm, node A currently holding the message forwards it based on the location of itself, its neighboring nodes and destination. We propose to use depth first search (DFS) method for routing decisions. Each node A, upon receiving the message for the first time, sorts all its neighbors according to a criterion, such as their distance to destination, and uses that order in DFS algorithm. It is the first localized algorithm that guarantees delivery for (connected) wireless networks modeled by arbitrary graphs, including inaccurate location information. We then propose the first localized QoS routing algorithm for wireless networks. It performs DFS routing algorithm after edges with insufficient bandwidth or insufficient connection time are deleted from the graph, and attempts to minimize hop count. This is also the first paper to apply GPS in QoS routing decisions, and to consider the connection time (estimated lifetime of a link) as a QoS criterion. The average length of measured QoS path in our experiments, obtained by DFS method, was between 1 and 1.34 times longer than the length of QoS path obtained by shortest path algorithm. The overhead is considerably reduced by applying the concept of internal nodes.

 

Volume 21, 2002, No. 2