Code Division Multiple Access Packet Radio Networks Research Articles

Optimal scheduling in cdma packet radio networks

Scope and Purpose—A packet radio network provides flexible data communication services among a large number of geographically distributed and mobile users (nodes). Organizing the multiple channel access in packet radio networks is a well known and widely discussed area. The time division multiple access (TDMA) technology has been popularly used and has been studied extensively. On the other hand, the development of the code division multiple access (CDMA) technology raises a new question in this field. In CDMA packet radio networks the channels can be realized by different orthogonal codes and the simultaneous reception of several packets is possible through the use of orthogonal codes. The multiple reception capacity provides an opportunity for significantly increasing system throughput. In this paper, we suggest an efficient heuristic algorithm for scheduling in CDMA packet radio networks. We consider the time slot assignment problem in a CDMA packet radio network. Unlike the classical TDMA packet radio networks, a CDMA packet radio network can provide each node with a multiple reception capacity using orthogonal codes. This multiple reception capacity of each node presents a new challenge for channel access protocols. Also we consider non-uniform traffic demand over nodes which has become important due to the increase of subscribers and the introduction of personal communication system (PCS). We present an algorithm for a general system where the number of nodes and the reception capacity can be any positive integers and the traffic demand can be non-uniform. Computational tests show that our algorithm generates excellent solutions in most cases.

A distributed link scheduling algorithm for CDMA packet radio networks

A distributed algorithm for the conflict-free channel allocation in CDMA (code division multiple access) networks is presented. Dynamic adjustment to topological changes is also considered. Though the schedules produced by our algorithm are not optimal with respect to link schedule length, the algorithm is simple and practical. The link schedule length minimization problem is NP-complete. Here the length of a link schedule is the number of time slots it uses. The algorithm guarantees a bound 2Δ — 1 time slots on the TDMA cycle length, where Δ is the maximum degree of a station (i.e., maximum number of stations that a station can reach by radio links) in the network. The message complexity of a station isO(Δ).

Admission policies for integrated voice and data traffic in CDMA packet radio networks

The authors derive optimal admission policies for integrated voice and data traffic in packet radio networks employing code division multiple access (CDMA) with direct-sequence spread spectrum (DS/SS) signaling. The network performance is measured in terms of the average blocking probability of voice calls and the average delay and packet loss probability of data messages. The admission scheme determines the number of newly arrived voice users that are accepted in the network so that the long-term blocking probability of voice calls is minimized. In addition, new data arrivals are rejected if the mean delay or the packet loss probability of data exceeds a desirable prespecified level. A semi-Markov decision process (SMDP) is used to model the system operation. Then, a value iteration algorithm is used to derive the optimal admission control. Two models for the other-user interference of the CDMA system are considered: one based on thresholds and another based on the graceful degradation of the CDMA system performance, and their performance is compared. These admission policies find application in emerging commercial CDMA packet radio networks including cellular networks, personal communication networks, and networks of LEO satellites for global communications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance analysis of spread spectrum packet radio network with channel load sensing

A continuous-time Markov-chain model for an asynchronous communication spread-spectrum code-division-multiple-access (CDMA) packet radio network is developed. The network is composed of mutually independent users. The receiver-based code is considered; a terminal with a packet to send looks up the destination's code and transmits on that code. Each user senses the channel load and refrains from transmission if the channel load exceeds the channel threshold. The model makes it possible to study the threshold effect of channel load on the performance of the CDMA packet radio network. Improvements in performance of spread-spectrum packet radio networks due to channel-load sensing are shown. Steady-state results for throughput are obtained. >