Channel allocation schemes

About: Channel allocation schemes is a research topic. Over the lifetime, 10656 publications have been published within this topic receiving 182117 citations.

Flexible channel allocation for a cellular system based on a hybrid of measurement-based dynamic channel assignment and a reuse-distance criterion algorithm

Abstract: In a cellular system, channels are assigned for new calls using a flexible channel allocation algorithm that is a hybrid of a measurement-based dynamic channel assignment (MBDCA) algorithm and a reuse-distance criterion algorithm, such as a cost-function-based DCA (CFBDCA). In one embodiment, the MBDCA algorithm is implemented at each cell site in the cellular system and generates a list of candidate channels for each new call. The list is transmitted to the mobile switching center (MSC), which implements the CFBDCA algorithm to select a particular channel from the list of candidate channels for the new call.

Reactive cognitive radio algorithms for co-existence between IEEE 802.11b and 802.16a networks

Abstract: This paper investigates the use of reactive cognitive radio algorithms to enable co-existence between IEEE 802.11b and 802.16a networks in the same unlicensed band. In particular, we develop a system model in which the two wireless systems share radio resources in frequency, space and time, and reactive coordination methods are used to reduce the mutual interference and improve link throughput. Reactive cognitive radio schemes utilize the available degrees of freedom in frequency, power and time, and react to observations in these dimensions to avoid interference. Dynamic frequency selection (DFS) enables radios to choose the band with the least interference. power control (PC) allows communications at the least possible transmit power. Time agility (TA) enables radios to adapt to each other's traffic patterns and avoid increasing interference in poor channel conditions. Simulation results are given for the following scenarios: (i) single 802.16a cell with single 802.11b hotspot; (ii) multiple 802.16a cells with multiple 802.11b hotspots. The results demonstrate that reactive cognitive radio schemes can provide significant improvements in 802.11b and/or 802.16a throughputs in the typical operating scenarios considered

Optimal skewed data allocation on multiple channels with flat broadcast per channel

Abstract: Broadcast is an efficient and scalable way of transmitting data to an unlimited number of clients that are listening to a channel. Cyclically broadcasting data over the channel is a basic scheduling technique, which is known as flat scheduling. When multiple channels are available, a data allocation technique is needed to assign data to channels. Partitioning data among channels in an unbalanced way, depending on data popularities, is an allocation technique known as skewed allocation. The problem of data broadcasting over multiple channels is considered, assuming skewed data allocation to channels and flat data scheduling per channel, with the objective of minimizing the average waiting time of the clients. First, several algorithms, based on dynamic programming, are presented which provide optimal solutions for N data items and K channels. Specifically, for data items with uniform lengths, an O(NK log N) time algorithm is proposed, which improves over the previously known O(N/sup 2/K) time algorithm. When K/spl les/4, a simpler O(N log N) time algorithm is exhibited which requires only O(N) time if the data items are sorted. Moreover, for data items with nonuniform lengths, it is shown that the problem is NP-hard when K=2 and strong NP-hard for arbitrary K. In the former case, a pseudopolynomial algorithm is discussed whose time is O(NZ), where Z is the sum of the data lengths. In the latter case, an algorithm is devised with time exponential in the maximum data length, which can optimally solve, in reasonable time, only small instances. For larger instances, a new heuristic is devised which is experimentally tested on some benchmarks whose popularities are characterized by Zipf distributions. Such experimental tests reveal that the new heuristic proposed here always outperforms the best previously known heuristic in terms of solution quality.

Distributed algorithms for dynamic channel allocation in microcellular systems

Abstract: The capacity of a microcellular system using dynamic channel allocation was studied. It was found that these systems can self-organize, with little loss in capacity, by using channel-allocation algorithms that are simple, practical, and local. The performances of both deterministic and probabilistic algorithms were calculated. Two classes of isotropic algorithms look particularly promising: the timid class, which is the simplest, and the aggressive class, which could provide improvements in system capacity and blocking probability. In particular, at the expense of additional rearrangements per call, these local algorithms can approach the capacity achieved by a global channel-allocation strategy. >

A review of OFDMA and single-carrier FDMA

Abstract: The debate on OFDM vs. single-carrier (SC) transmission started back in the 1980s at the time of the European Digital Audio Broadcasting (DAB) and Digital Video Broadcasting (DVB) projects. The same questions arose later in wireless communications, and OFDM transmission with TDMA was adopted in the IEEE 802.11a specifications for wireless local area networks and by the WiMAX Forum for fixed WiMAX systems. Later, orthogonal frequency-division multiple access (OFDMA) was adopted by the WiMAX Forum for mobile WiMAX systems and more recently by the 3GPP for the downlink of Long Term Evolution (LTE) systems. In contrast, single-carrier FDMA was adopted for the uplink of LTE. In this overview paper, we will review these historic developments and give some recent results on OFDMA and Single-Carrier FDMA.