Number Of Idle Channels Research Articles

Joint bandwidth and power allocation for multiple services in TV white space

As the bandwidth resource in TV white space (TVWS) is permitted to be used for the secondary users, multiple secondary networks coexisting in the same geographical area can provide multiple services without interfering with the primary service, such as the TV broadcasting. To satisfy the minimum rate requirements and maximise the sum rate of the multiple services, the problem of resource allocation can be modelled as a mixed integer non-linear programming (MINLP). According to this model, the joint bandwidth and power allocation (JBPA) method is proposed to solve the resource allocation for multiple services. The JBPA method is sub-optimal, which can approximate the performance of the optimal two-step exhaustive search (TSES) method very well, especially when the number of services is larger than the number of idle channels. Compared with TSES, the JBPA method decreases the complexity from exponential level to polynomial level. Besides, compared with one channel occupied by single service, the JBPA can serve more services and provide stable performance when the number of services varies dynamically. Compared with the algorithm random bandwidth allocation, the JBPA can approximate the optimal performance provided by TSES better with the time complexity of the same order.

Distributed Transmission Control in Multichannel S-ALOHA for Ad-Hoc Networks

Wireless ad-hoc networks are marked without a basic infrastructure and global information for the current status of the network. For multichannel slotted ALOHA systems of wireless ad-hoc networks, this letter proposes a (re)transmission control algorithm for the transmitters to employ. The algorithm aims at minimizing Lyapunov (negative) drift on the sum of all transmitters’ queue, while it is implemented in a distributed way such that each transmitter only needs local information, such as the number of idle channels. To control (re)transmission probability optimally, with the local information, each transmitter solves a subproblem of estimating the number of backlogged nodes in each time slot. Simulation results show that our proposed algorithm yields near-optimal queuing performance.

A Study on Channel Sharing for Congestion Control in WSN MAC Protocols

Congestion control in Wireless Sensor Networks (WSNs) has been an area of interest for researchers for ensuring timely delivery of data. A number of Multi-channel MAC protocols have been proposed which guarantee parallel and collision free transmissions. This article proposes to evaluate an existing congestion control scheme that was developed for multi-channel WSN MAC protocols dealing with traffic of different priorities. The existing scheme proposed prioritized channel sharing mechanism for nodes based on the Received Signal Strength (RSS) of each priority. The authors analyze the performance of the proposed scheme by comparing it with other channel sharing mechanisms. Four cases of hybrid channel sharing mechanisms, namely complete partitioning, complete sharing, partial sharing and prioritized sharing have been studied in this work for 2 traffic priorities. The authors have modeled the schemes for WSN applications where each node may have traffic of different priorities. Major objective of the article is to facilitate the high-priority traffic, while efficiently maintaining the network utilization through reducing the number of idle channels. The analytical model has been developed using 2-dimensional Continuous Time Markov Chains (CTMC), and MATLAB has been used for the implementation. Complete sharing and Prioritized sharing are found to be the most efficient channel sharing schemes based on the network utilization and total throughput.

Multiserver Queue with Guard Channel for Priority and Retrial Customers

This paper considers a retrial queueing model where a group of guard channels is reserved for priority and retrial customers. Priority and normal customers arrive at the system according to two distinct Poisson processes. Priority customers are accepted if there is an idle channel upon arrival while normal customers are accepted if and only if the number of idle channels is larger than the number of guard channels. Blocked customers (priority or normal) join a virtual orbit and repeat their attempts in a later time. Customers from the orbit (retrial customers) are accepted if there is an idle channel available upon arrival. We formulate the queueing system using a level dependent quasi-birth-and-death (QBD) process. We obtain a Taylor series expansion for the nonzero elements of the rate matrices of the level dependent QBD process. Using the expansion results, we obtain an asymptotic upper bound for the joint stationary distribution of the number of busy channels and that of customers in the orbit. Furthermore, we develop an efficient numerical algorithm to calculate the joint stationary distribution.

Throughput Analysis for a Multi-User, Multi-Channel ALOHA Cognitive Radio System

In this paper, we investigate a novel slotted ALOHA-based distributed access cognitive network in which a secondary user (SU) selects a random subset of channels for sensing, detects an idle (unused by licensed users) subset therein, and transmits in any one of those detected idle channels. First, we derive a range for the number of channels to be sensed per SU access. Then, the analytical average system throughput is attained for cases where the number of idle channels is a random variable. Based on that, a relationship between the average system throughput and the number of sensing channels is attained. Subsequently, a joint optimization problem is formulated in order to maximize average system throughput. The analytical results are validated by substantial simulations.

Algorithmic approach to studying models of multirate systems with queues

Models of multirate systems that handle narrowband and broadband calls are investigated. Narrowband calls are serviced by a single channel, whereas m > 1 channels are required simultaneously for broadband calls. When the necessary number of idle channels is absent, broadband calls are queued but narrowband calls are not buffered and are accepted only if the number of idle channels is larger than a given threshold. An algorithmic approach is proposed to the calculation of service quality indices for such models, and results of numerical experiments are presented.

A Dynamic Channel Assignment Algorithm for High Capacity Microwave Mobile Communication Systems

In this paper, a dynamic channel assignment scheme is proposed. In this scheme, when a call originates in a high capacity network cell, and if all the channels in it are busy, it looks for a channel to be borrowed from the neighboring cell, which has most number of idle channels. If the cell has to borrow a channel from any of its neighboring cell then the particular channel has to be blocked in the re-use cells. But geographically it is enough if it blocks the channel in two co-channel cells, where the co-channel interference is pronounced. This deals to the concept of Borrowed Channel allocation with Directional Locking. The aim of the paper is to find the difficulties in lending a channel to a neighboring cell and thus develop an algorithm which overcomes the restrictions imposed by this new channel allocation scheme.

Simple prioritized protocol for multi-channelp-persistent CSMA/CD networks

This paper presents and investigates a new prioritized protocol for p-persistent CSMA/CD multi-channel local area networks in which the transmission medium consists of a number of time-multiplexed or frequency-multiplexed channels. Priority access with this protocol is obtained through making the packet transmission probability a function of the message priority as well as the number of idle channels sensed in the multi-channel network. By simply changing this function without modifying the underlying multi-access mechanism, the new protocol is found to be very effective in providing a wide spectrum of performance variation for different priority users.

Simple priority scheme for multichannel CSMA/CD local area networks

This paper describes and analyses a new priority CSMA/CD protocol for multichannel local area networks. In this scheme, low priority messages can be transmitted by using the CSMA/CD protocol only when the number of idle channels exceeds a certain value. Following a general description of the proposed priority protocol, this paper analyses the protocol by first formulating the various state transition probabilities of the network. The delay and throughput characteristics of the various priority messages are then calculated and presented. It is found that the performance of this simple scheme is comparable to the priority schemes studies in Reference 8 for CSMA/CD networks. Also, in order not to starve off low priority stations, the largest number of idle channels when the transmission of low priority packets becomes inhibited should not be more than about one third of the total number of channels.