A code allocation protocol for maximizing throughput in CDMA based ad hoc networks (original) (raw)

Distributed resource allocation for DS-CDMA-based multimedia ad hoc wireless LANs

IEEE Journal on Selected Areas in Communications, 1999

Power control in direct sequence-coded vision multiple access (DS-CDMA) systems and, more recently, power/rate allocation in multirate DS-CDMA based networks is an open and interesting research area which has attracted much attention. However, with a few exceptions, most researchers have emphasized centralized resource allocation algorithms for cellular systems where the base station keeps track of the requirements of the various users and is thus responsible for the management of network resources. Ad hoc wireless local area networks (WLAN's), on the other hand, are generally configured as peerto-peer networks with no centralized hub or controller. Thus resource allocation has to be conducted in a distributed fashion. We address the issue of distributed resource management for multirate DS-CDMA based multimedia WLAN's by 1) presenting a distributed resource allocation protocol, known as distributed resource negotiation protocol (DRNP) that builds on the RTS/CTS bandwidth reservation mechanism provided by IEEE 802.111, and provides quality of service (QoS) guarantees through distributed control of resources in DS-CDMA based multimedia WLAN's and 2) investigating the performance of various resource allocation schemes within the context of DRNP, in terms of network wide metrics such as overall throughput and blocking rates.

Downlink Throughput Maximization in CDMA Wireless Networks

IEEE Transactions on Wireless Communications, 2000

We investigate optimum rate assignment scheme maximizing network throughput on the downlink of a multirate CDMA wireless network. Systems employing orthogonal variable spreading factor (OVSF) codes as well as systems employing multiple codes have been studied. Our objective is to maximize the network throughput under constraints on total transmit power, total bandwidth and individual QoS requirements specified in terms of minimum rates. First, users are ordered based on their transmit energy per bit requirements to achieve the target received energy per bit to interference power spectral density ratio at the receivers. Based on the initial ordering, we prove that for systems employing multiple codes, greedy rate scheduling yields maximum network throughput. For systems employing variable spreading codes, we show that greedy rate scheduling is optimal if the minimum rate requirement of a user is larger than or equal to the minimum rate requirement of any other user with a larger transmit energy per bit requirement. Simulation results verify the superiority of the greedy algorithm under various system and channel assumptions.

Cross-Layer Design for Medium Access Control in CDMA Ad Hoc Networks

EURASIP Journal on Advances in Signal Processing, 2005

A medium access control (MAC) protocol for spread-spectrum ad hoc networks with dynamic channel allocation (DCA) is presented. DCA can support large systems with a smaller number of channels by dynamically assigning channels only when a node has a packet to transmit. The protocol extends cross layer, with the scheduling at the MAC, and assignment of channels at the physical layer by means of a query. It is shown that DCA is collision free under ideal conditions. By assigning channels dynamically, DCA offers improved throughput normalized by available bandwidth. Analytical results are presented for the performance of the query detection and the throughput for a fully connected network.

Capacity Optimization in TDMA Ad-Hoc Networks

Wireless Personal Communications

Many scheduling techniques have been developed to solve the problem of sharing the common channel to multiple stations. TDMA has been increasingly used as a scheduling technique in ad-hoc networks. The current trend for QoS capable applications led to the deployment of numerous routing schemes that use TDMA. These schemes try to solve the problem of distributing the available slots among the wireless nodes and at the same time, to find paths within the network that fulfill some QoS related limitations, such as end-to-end delay. The exact way the slots are distributed among the transmitting nodes has an impact on the end-to-end delay and other performance parameters of the network, such as capacity. Therefore, the efficiency of the scheduling algorithms is closely related to the network topologies. In this paper, we propose two new end-to-end TDMA scheduling algorithms that try to enhance the network capacity by increasing the number of concurrent connections established in the network, without causing additional end-to-end delay. We study the efficiency of the proposed algorithms, when applied on various random topologies, and compare them in terms of end-to-end delay and network capacity.

Transmission capacity of CDMA ad-hoc networks

Eighth IEEE International Symposium on Spread Spectrum Techniques and Applications - Programme and Book of Abstracts (IEEE Cat. No.04TH8738)

Spread spectrum technologies are appropriate for ad hoc networking because they permit interference averaging and tolerate co-located simultaneous transmissions. We develop analytic results on the transmission capacity of a CDMA ad hoc network. Transmission capacity is defined as the maximum permissible density of simultaneous transmissions that allows a certain probability of successful reception. Three models of increasing generality are analyzed: a trivial model with two transmitters, a Poisson point process model where each node transmits with fixed power, and a Poisson point process model where nodes use variable transmission powers. We obtain upper and lower bounds on the transmission capacity for both frequency hopped (FH-CDMA) and direct sequence (DS-CDMA) implementations of CDMA for the latter two models. Our analysis shows that FH-CDMA obtains a higher transmission capacity than DS-CDMA on the order of M 1− 2 α , where M is the spreading factor and α > 2 is the path loss exponent. The interpretation is that FH-CDMA is generally preferable to DS-CDMA for ad hoc networks, particulary when the path loss exponent is large.

A Cdma Route Protocol for Ad Hoc Wireless Networks

International Conference on Aerospace Sciences and Aviation Technology

A Mobile ad hoc network is a collection of wireless nodes, all of which may be mobile, laptop , personal digital assistants, that dynamically create a network without using any infrastructure. Each host participating in the network acts both as a host and as a router. As mobile hosts are no longer just end systems; each node must be able to function as a router as well as to relay packets generated by other nodes. As the nodes move in and out with respect to each other, the resulting changed topology must somehow be able to communicate to all other nodes as appropriate. In such networks, it is of a special importance to grantee Quality of Service (QoS), such as packet loss and bandwidth. To accomplish this, an admission control scheme which guarantee bandwidth for real-time applications in multihop mobile ad hoc networks is developed. In this scheme there is end-to-end bandwidth calculation and bandwidth allocation. To perform this objective, the source is informed of the bandwidth and QoS available to any destination in the network to enable the establishment of QoS connections and the efficient support of real time applications in the network. Simulation results showed distinct performance advantages of the introduced protocol over those reported previously.

Scheduling Using Near-optimal Guard Zones for CDMA Ad Hoc Networks

2006 IEEE International Conference on Communications, 2006

Scheduling algorithms in ad hoc networks allow nodes to share the wireless channel so that concurrent transmissions can be decoded successfully. On one hand, the scheduling needs to be efficient to maximize the spatial reuse and minimize retransmissions due to collisions. But on the other hand, due to the very nature of uncentralized wireless networks, the scheduling algorithm needs to easily implementable in a distributed fashion with little, if any, coordination with other nodes in the network. The goal of this paper is to propose and evaluate a simple scheduling technique based on receiver guard zones. In particular, using stochastic geometry, we show that a near-optimal guard zone can easily be realized in a distributed manner, and that this has about a 2 − 100x increase in capacity as compared to an ALOHA network; the capacity increase depending primarily on the required outage probability , as lower tolerances increasingly reward scheduling. By implementing guard zone-based scheduling, we show that the attained performance is about 70 − 80% of a well-known nearoptimal (and practically infeasible) centralized scheme.

Code assignments in CDMA networks: distributed algorithms and genetic algorithm heuristics

1998

CDMA is an important spread spectrum communication technology for wireless and mobile networks. We investigate the code assignment probl e m o n a C D M A n e t work with hidden terminal interference, which h a s b e e n proven to be NP-hard. Our major contributions include: (1) A dynamic distributed code assignment algorithm which w e b e l i e v e is the rst one to appear in the literature. By formal analysis, we p r o ve that the algorithm is correct: it is deadlock-free, assigns valid codes to newly arriving nodes within xed maximum delay, and maintains consistent topology information throughout the network. (2) New centralized heuristics based on genetic algorithms (GA). Experiments are performed on 37 test graphs. For each graph, the GA heuristics perform at least as good as, and in many instances better than, the best result obtained from 1,000 runs of the greedy algorithm.

Assigning Codes in a Random Wireless Network

Lecture Notes in Computer Science, 2004

In this paper we present an algorithm that can assign codes in the Code Division Multiple Access (CDMA) framework for multihop ad hoc wireless networks. In CDMA framework, collisions are eliminated by assigning orthogonal codes to the stations such that the spectrum of frequency can be used by all transmitters of the network at the same time. In our setting, a large number n of distinguishable stations (e.g. sensors) are randomly deployed in a given area of size |S|. We propose an efficient and fully distributed algorithm, which assigns codes to the nodes of our network so that, for any ℓ > 0, any two stations at distance at most p (1 + ℓ) |S| log n/π n from each other are assigned two distinct codes.

An Efficient Single-Transceiver CDMA-Based MAC Protocol for Wireless Networks

IEEE INFOCOM 2007 - 26th IEEE International Conference on Computer Communications, 2007

Applying the code division multiple access (CDMA) techniques, we propose an efficient medium access control (MAC) protocol with single-transceiver for wireless ad hoc networks. Our protocol adopts the time-division method to solve the near-far power control problem inherently associated with the CDMAbased networks. In particular, employing the variable ad-hoc traffic indication messages (ATIM) window to properly determine the required transmission power for data packets, our scheme enables the interference-limited simultaneous transmissions to achieve the high utilization of the limited/precious bandwidth in wireless networks. In addition, our scheme requires only one transceiver per node, which reduces the hardware costs for large scale wireless networks. Using the Markov-chain techniques, we develop an analytical model to evaluate the aggregate throughput under our protocol. Both the analytical and simulation results show that our protocol can improve the network throughput significantly as compared with other existing schemes. Index Terms-Code division multiple access (CDMA), Markov chain, medium access control (MAC), near-far problem, wireless networks.