Elsevier

Ad Hoc Networks

Volume 3, Issue 6, November 2005, Pages 689-701
Ad Hoc Networks

Bandwidth guaranteed call admission in TDMA/CDMA ad hoc wireless networks

https://doi.org/10.1016/j.adhoc.2004.01.002Get rights and content

Abstract

This paper first studied the timeslot assignment problem in time division multiple access/code division multiple access (TDMA/CDMA) wireless ad hoc networks. Given a path P, we prove that a timeslot assignment providing one unit of bandwidth on P can be found in O(∣P∣) time if such an assignment exists. The results have been extended to the case that P can provide two units of bandwidth. Based on the timeslot assignment for the special cases, an efficient slot assignment algorithm with O(∣P∣2k) is proposed for general cases, where k is the number of slots in a TDMA frame. Then, the timeslot assignment algorithm is integrated into a quality of service (QoS) call admission scheme for QoS call requests. Extensive simulations are conducted and the results have demonstrated the superior performance of our method.

Introduction

An ad hoc network consists of a set of wireless nodes that are equipped with transmitters and receivers (transceivers). There is no wired infrastructure to support communication among these mobile nodes, and each node in the network is a router as well as a communication end-point. Much research has been done in ad hoc networks. Quality of service (QoS) guaranteed service is one of the important topics and has received a lot of attention recently [2], [10], [11], [15], [16].

There are several parameters of QoS, such as interference ratio, packet loss rate, delay, bandwidth, etc. We focus our discussion on “bandwidth” in this paper, because it is one of the most critical requirements for real time application. In QoS guaranteed communication, call admission is required for call setup and resource reservation. Some works have been done in call admission control. A complete admission control scheme incorporating timeslot assignment algorithm was proposed [3]. Jia et al. [4] discussed a multicast routing in admission control mechanism. A distributed admission control architecture to support core-stateless guaranteed services was proposed [13]. In this paper, we discuss the routing and bandwidth reservation for a QoS call in ad hoc networks.

We assume the time division multiple access (TDMA) scheme is used at MAC layer as bandwidth reservation for calls. In the TDMA structure, the bandwidth at a node is partitioned into a set of timeslots that are grouped into a frame. A node equipped with a transceiver can either transmit or receive at a timeslot, but not to do the both simultaneously. When a node transmits signals to a neighbor node at a timeslot, the neighbor node must listen to this node and receive its signals at the same timeslot. That is, transmission and reception between a pair of neighbor nodes must occur in the same timeslot.

Timeslot assignment for a call is to reserve timeslots at each node along the route of the call. Its purpose is to meet the bandwidth requirement of the call. Without a proper slot assignment, a call may not be able to be admitted, even there exists enough free timeslots for the call in the system. Lin and Liu presented a sequential assignment algorithm [2], where timeslots are reserved node by node from the source towards the destination, and at each node, slots that are not available in the next down-stream node are first reserved. Lin’s timeslot assignment method was extended to finding multiple QoS paths for fault tolerance in [6]. Another sequential assignment method was proposed in [9], and at each node, the algorithm first calculated common slots among the node, its up-stream node and its down-stream node, then assigned half of the common slots to this node for transferring and others for receiving. The existing works in timeslot assignment usually employ hop-by-hop reservation scheme, which lacks a global view of slot availability on the whole path. None of them can guarantee to find a path with requested bandwidth if such a path does exist.

Our main contribution in the paper is that we propose an efficient timeslot assignment algorithm from a global view. The algorithm is optimal for the case that a call requests only one unit of bandwidth. Our method can also guarantee to find an assignment that provides at lest two units of bandwidth if there exists an assignment that can give three units of bandwidth in the system. Following the solutions to the special cases, an efficient slot assignment algorithm was proposed for general cases, and simulation results have shown the superior performance of our method.

Section snippets

System model and problem specification

The ad hoc wireless network is modeled by an undirected graph G(V,E), where V represents a set of n wireless nodes distributed in an area (i.e. ∣V∣ = n) and E a set of links of the network. Notice that links in the network are assumed to be symmetric. We further assume that there are k timeslots in a frame and the slots are numbered from 0 to k  1 in the same way at all nodes. All nodes in the system have synchronized clocks that allow them to synchronize the transmission and reception at

Timeslot assignment for special cases

We first consider some special cases of timeslot assignment over a path where a call requests one or two units of bandwidth. Then, we extend the result to the general case in the next section.

The following lemma states the necessary condition where one unit of bandwidth can be found on a path.

Lemma 1

Given a path P, if every link on P has at least two units of bandwidth except for one link which has at least one unit of bandwidth, then an assignment αP making BW(P,αP) = 1 can be found.

Proof

We first consider

Timeslot assignment for general cases

This section considers the general case of bandwidth guaranteed QoS calls.

Illuminated by Theorem 1, Theorem 2, we believe that first assigning the links with the least free slots is a good strategy in timeslot assignment on a path P. Assume that a QoS call requests b units of bandwidth. Similar to the special cases in Theorem 1, Theorem 2, we first sort all links in P in ascending order according to the number of free slots. Then, each time we choose the link with least number of free slots

Integrated algorithm for call admission

We now integrate our timeslot assignment algorithms into a QoS routing protocol.

Most routing protocols in ad hoc networks can be categorized as pro-active (using routing tables, such as DSDV [8]) and on-demand protocols (e.g., DSR [5], AODV [14]). In the pro-active protocols, each node maintains a routing table and periodically exchanges routing information by broadcast for update. There is no need to keep routing tables in on-demand protocols. A route discovery is activated only when necessary

Simulation

The main purpose of timeslot assignment on a path is to meet the QoS requirement. An efficient timeslot assignment algorithm can find an assignment that meets the bandwidth requirement in many cases. So we use success ratio to measure the effectiveness of timeslot assignment algorithms, which is defined as the following:Successratio=ThenumberofsuccessfulrequestsThenumberoftotalrequests×100%.Furthermore, a good timeslot assignment algorithm should find enough candidate paths for reservation,

Conclusions

Timeslot assignment problem in TDMA/CDMA wireless ad hoc networks has been studied in this paper. First, Given a path P, we proved that a timeslot assignment providing one unit of bandwidth on P can be found in O(∣P∣) time if such an assignment exists. Then we extended the theorem that an assignment that provides at least two units of bandwidth can be found in O(∣P∣) time if there exists an assignment that gives three units of bandwidth on P. Following the solutions to the special cases, we

Acknowledgement

This work is supported by project no. 7001297 and CityU 1079/02E.

Hai Liu received his B.Sc. (1999) and M.Sc. (2002) in Applied Mathematics, South China University of Technology, China. He is currently a Ph.D. candidate in Department of Computer Science at City University of Hong Kong. His research interests include distributed systems, wireless networks and mobile computing.

References (17)

  • L. Hu

    Distributed code assignment for CDMA packet radio networks

    IEEE/ACM Transactions on Networking

    (1993)
  • C.R. Lin et al.

    QoS routing in ad hoc wireless networks

    IEEE Journal on Selected Areas in Communications

    (1999)
  • C.R. Lin

    Admission control in time-slotted multihop mobile networks

    IEEE Journal on Selected Areas in Communications

    (2001)
  • X. Jia et al.

    An integrated routing and admission control mechanism for real-time multicast connections in ATM networks

    IEEE Transactions on Communications

    (2001)
  • D.B. Johnson et al.

    DSR: the dynamic source routing protocol for multi-hop wireless ad hoc networks

  • Y.-S. Chen, Y.-W. Ko, T.-L. Lin, A lantern-tree-based QoS multicast protocol for wireless ad-hoc networks, in: IEEE...
  • M.R. Gary et al.

    Computers and Intractability

    (1979)
  • C.E. Perkins, P. Bhagwat, Highly dynamic destination-sequenced distance-vector routing (DSDV) for mobile computers, in:...
There are more references available in the full text version of this article.

Cited by (10)

View all citing articles on Scopus

Hai Liu received his B.Sc. (1999) and M.Sc. (2002) in Applied Mathematics, South China University of Technology, China. He is currently a Ph.D. candidate in Department of Computer Science at City University of Hong Kong. His research interests include distributed systems, wireless networks and mobile computing.

Xiaohua Jia received his B.Sc. (1984) and M.Eng. (1987) from the University of Science and Technology of China, and obtained his D.Sc. (1991) in Information Science from the University of Tokyo, Japan. He is currently associated with Department of Computer Science at City University of Hong Kong. His research interests include distributed systems, computer networks, WDM optical networks, and Internet and mobile computing.

Deying Li received her M.Sc. (1988) in Mathematics from Central China Normal University, China, and obtained her D.Sc. (2003) in Computer Science from City University of Hong Kong. She is an associate professor in School of Information, Renmin University of China. Her research interests include computer networks, WDM optical networks, and Internet and mobile computing and design of optimization algorithms.

C.H. Lee obtained degree in Electrical Science from the State University of New York and an M.Math. from the University of Waterloo. He has been involved in the communication and networking since the early 1980s when he was at Northern Telecom’s Research laboratory in Ottawa, Canada, participating in voice and data Network Design and Development. He joined the Department of Computer Science at City University of Hong Kong in 1987. His research interests are in the areas of Computer Networks and Distributed Systems. He also participates in consultancy work on network design, analysis and testing for major infrastructural projects. He is a member and a past chairman of the IEEE Computer Society, Hong Kong.

View full text