Channel Reallocation Research Articles

Influence of power control in the mobile network on the radiation level

Abstract The paper evaluates how the control of transmitted power affects the intensity of radiation in a mobile network cell. Cell models without power control, with standard power control and a model with power control and channel reallocation are considered. The relative reduction of radiation is evaluated and several examples of calculations are presented. Remarks are given on the dependence of radiation reduction on the number of traffic channels, traffic intensity and signal attenuation coefficient. The assessment procedure and results are based on previously verified traffic process simulation models.

2.4GHz Wireless Local Area Network Optimization in University Dormitory Buildings

This article describes the wireless network problems met in University dormitory buildings, especially under 2.4GHz spectrum. Through wireless network optimization such as channel re-allocation and transmission power adjustment manually, the performance of the wireless LAN could be improved a lot even for real-time services such as video and live broadcast.

Energy Aware Channel Allocation with Spectrum Sensing in Pilot Contamination Analysis for Cognitive Radio Networks

Cognitive radio (CR) is an innovative and contemporary technology that has been making an effort to overcome the problems of bandwidth reduction by rising the usage of mobile cellular bandwidth connections. The reallocation and distribution of channels is a fundamental characteristic of cellular mobile networks (CMN) to exploit the consumption of CMS. Meanwhile, throughput maximization might lead to higher power utilization, the spectrum sensing system must tackle the energy throughput tradeoff. The spectrum sensing time should be defined by the residual battery energy of secondary user (SU). In that context, energy effective algorithm for spectrum sensing should be developed for meeting the energy constraint of CRN. This study designs a new quantum particle swarm optimization-based energy aware spectrum sensing scheme (QPSO-EASSS) for CRNs. Here, the presented QPSO-EASSS technique dynamically estimates the sensing time depending upon the battery energy level of SUs and the transmission power can be computed based on the battery energy level and PU signal of the SUs. In addition, in this work, the QPSO-EASSS technique applies the QPSO algorithm for throughput maximization with energy constraints in the CRN. The detailed set of experimentations take place and reported the improvements of the QPSO-EASSS technique compared to existing models.

Estimation of Traffic Influence on Energy Saving at GSM Channels with Reallocation

This paper presents an innovative procedure for base station emission power calculation in the case of traffic channels reallocation implementation in GSM mobile systems. The main idea of active traffic channels reallocation is to place the connections which require higher emission power due to higher mutual distance between base station and mobile station to the first frequency carrier because these channels have to be always in active mode due to the applied discipline of traffic service in GSM mobile systems. The principle of connections reallocation on the base of distance values sequence determination is novelty comparing to the much more applied principle of connections arrangement according to the propagation conditions. Power saving as the result of this method usage is compared to the necessary power when the sequential hunting with homing method of idle channel looking for is applied. Two special cases are analyzed: 1. the case of low offered traffic (when not more than 6 traffic channels are busy on average) and the case when offered traffic is increased. It is proved that the achieved relative energy saving when the offered traffic is increased over 6Erl rapidly grows at first and then begins to fall. It is important that the absolute value of power saving continuously increases when the offered traffic is increased. One typical example of base station emission power save daily profile is presented on the base of the obtained results.

Optimal Spectrum Allocation Based on Primary User Activity Model in Cognitive Radio Wireless Sensor Networks

In Cognitive Radio Wireless Sensor Networks, the licensed spectrum bands are highly dynamic, and their status varies overtime. With the expansion of these networks, regarding the energy constraints and the fact that reallocation of the frequency spectrum is energy-consuming, the problem of controlling the behavior of secondary users in the allocation of the spectrum is of great importance. Providing a method to reduce the number of channel reallocation, which in turn results in reducing energy consumption in such a dynamical network is essential. In this paper, considering the energy constraints, an optimal method for allocating frequency spectrum resources is presented using game theory and Nash equilibrium. By analyzing the activity model of primary users on the frequency spectrum and selecting the appropriate spectrum using the Nash equilibrium, the method reaches the network to a stationary equilibrium point. In these conditions, in addition to reducing interference between primary and secondary users, the number of channel reallocations by cognitive radio users is reduced and thus reduces overall energy consumption in the network and increases its life span.

DVB-T Receiver Independent of Channel Allocation, With Frequency Offset Compensation for Improving Resolution in Low Cost Passive Radar

In this article, a commercial low cost solution for increasing DVB-T based passive radar (also referred to as passive coherent location) robustness with respect to channel allocation and range resolution, is designed. IDEPAR demonstrator is updated to include a new recording system in charge of DVB-T channels reallocation. The use of commercial hardware introduces frequency mismatching between acquired channels that compromises system operation. To face channel frequency alignment, fulfilling the requirements imposed by the high Doppler resolution typical of passive radars, a novel compensation algorithm is proposed, based on the minimization of signal dispersion in the Cross-Ambiguity Function domain. The well-known cyclic prefix van de Beek method is used as reference. Results show an increase in target signal to interference ratio and detection performances, as well as a reduction of clutter dispersion when the novel proposed algorithm is applied. The low cost solution is also compared to a high performance one capable of acquiring a wide bandwidth of sparse DVB-T channels, and performing channel reallocation by digital signal processing. Results show that both systems reached similar performances in terms of range resolution and SNR improvement.

Power saving technique based on traffic channels reallocation in GSM mobile network

Abstract A mobile users’ network with power control on traffic channels, as it is GSM, is considered in this paper. It is analyzed the influence of busy channels reallocation on the necessary emission power. The main principle in reallocation is that users who need greatest power for their connections take traffic channels of the first carrier where power is always maximum. It is assessed that reallocation process is not more complicate than the simplest handover processes. It is proved that this method may be used to decrease emission power of carriers after the second one. Power saving depends on number of carriers, environmental propagation coefficient and users’ density distribution in the cell. The results are verified by originally developed simulation program.

Channel allocation in cognitive radio networks using energy detection technique

Cognitive radio (CR) is a modern and innovative technology that seeks to solve this issue of bandwidth depletion by increasing the use of the mobile cellular connectivity bandwidth. The distribution and re-allocation of channels is a crucial aspect of cellular mobile networks (CMNs) to maximize the utilization of the CMS. This work reviews the transmitter based cognitive radio (CR) techniques and analysis them based on signal to noise ratio. This paper also proposes a complete model for energy detection. The analysis and simulation are carried out in Matlab by taking BPSK and QPSK modulation. This energy detection has the advantages as no prior knowledge of the primary consumer is needed and this system's computational cost is very small.

Refining channel and power allocation for green device-to-device communications

Most of the existing researches for D2D communications try to achieve the minimum total transmission power of D2D user devices (DUEs) by performing channel assignment first, and then performing power control according to the QoS requirement of each DUE. However, after power control, the transmission powers and interferences of DUEs have dropped and the qualities of channels have changed, hence there is room to further reduce the transmission power of DUEs. To improve the existing works, the channel and power reallocations are performed for several rounds in the proposed schemes until the dropping transmission power is less than a threshold. Note that, the channel and power are not really allocated to the DUEs until the final refining allocation results are calculated by the base station. The trade-off among transmission power, throughput, and computation cost are discussed through extensive simulations. Simulation results justify the energy efficiency of the proposed refining schemes.

User re-association and resource/power re-allocation of cell switched-off User Equipments in green cellular networks

Energy consumption of cellular networks has gained significant attention in recent years as green cellular networking paradigm appeared. Base Station (BS) switch-off is a solution for minimizing energy consumption of green cellular networks. However, User Equipments (UEs) of switched-off BSs lose their connectivity to the network and should be re-associated with BSs, attain new radio resources, and re-adjust their transmission powers. Previous studies have either not addressed this issue or have considered the joint problem of BS switch-off and BS association/resource allocation, while those joint problems are not spectrum efficient. In this paper, we formulate two different optimization problems for spectrum efficient re-association of involved UEs and re-allocation of their uplink radio/power resources after an energy-efficient BS switch-off. The first optimization problem aims at maximizing the achievable rate of cell switched-off UEs, while the second problem intends to maximize the achievable rate of all UEs of the network when a cell switch-off occurs. In formulated problems, the required rate of UEs is regarded as the QoS constraint. Decoupling the problems into sub-problems, we propose a distributed solution for user re-association, channel re-allocation, and power adjustment of UEs. Simulation results show superior performance of the proposed methods compared to the baseline methods in terms of the network capacity and QoS guarantee.

Distributed allocation and dynamic reassignment of channels in UAV networks for wireless coverage

Providing wireless coverage to users using Unmanned Aerial Vehicles (UAVs) encounters two major challenges: deployment and channel allocation. To this end, solutions to both issues are proposed in this paper. An overloaded UAV attempts to acquire more channels by performing channel bonding/aggregation followed by requesting its chosen peers to move closer for load sharing. The proposed channel reallocation schemes minimize interference caused by channel reassignments, or change in network topology. The simulation results show that when employing these schemes, more data is served with reduced discontinuous service time and efficient usage of limited battery power.

Beam wander relieved optical switch using Bessel beams in turbulent atmosphere

The digital micro-mirror device (DMD)-based optical switch has the advantages of high-speed channels reallocation, miniaturization, stability, and large capacity for short reach optical communication in the datacenter. However, thermal turbulent atmosphere in the datacenter would cause perturbations and channel crosstalk for the optical switch. The self-healing optical beams such as the Bessel beams have the non-diffraction property to mitigate the turbulence issue. Here, we propose and demonstrate a Bessel beams enabled DMD-based optical switch to improve the stability and performance of optical communication in turbulent atmosphere. We statistically characterize the beam wanders of the Gaussian and Bessel beams in turbulent atmosphere at temperatures of 60°C and 80°C. We build the two-channel optical switch communication system and measure the bit error rate of the 15 Gbit/s on–off keying signals transmitted by the Gaussian and Bessel beams at temperatures of 60°C and 80°C, respectively. The optical switch using the Bessel beams shows lower bit error rates with weaker fluctuations compared with the Gaussian beams. The DMD-based optical switch using the Bessel beams has the potential for practical optical communication applications in the datacenter.

Traffic aware channel assignment with node stability in wireless mesh networks

In a wireless network the most challenging issue is Channel assignment. The channel assignment problem is codependent with the routing problem. We need to compute again the channel assignment as and when the traffic pattern changes. Anyways, previously followed channel assignment algorithms will assign channels from scratch. It will end up with an entirely dissimilar configuration of nodes; in turn it will disturb the action of the particular network. It takes little time to create links and to establish new channels. This time is significant in assigning links for wireless networks. This leads to channel reassignment. This algorithm considers the existing channel assignment and tries to go along with the new stream of traffic flow design in the finest possible way by changing the channel on a restricted number of radios. In order to provide node stability, we used entropy function. In this paper, we demonstrate a channel reallocation algorithm with node permanency and appraise its performance by using NS2. Experimental outcomes show that the node stability can progress the performance of network when compared with the earlier methods.

Micro-Grating Array-Enabled Power Efficiency Improvement for a DMD-Based Optical Switch

Digital micro-mirror device (DMD)-based optical switch can dynamically change the channels reallocation and provide flexibility in optical networking with the advantages of fast time response and scalable port number. However, the DMD as a binary diffraction device has a limited efficiency of 10.1% at the +1st diffraction order. Here we propose and demonstrate a DMD-based optical switch with improved efficiency enabled by a blazed micro-grating array. The blazed micro-grating array is designed and fabricated to diffract and make use of the wasted −1st order beams of the DMD. Using this device, we achieve ~2 dB efficiency improvements for a $2\times 2$ optical switch with all switching states. We experimentally demonstrate high speed switching of channels carrying 15 and 30 Gb/s ON-OFF keying signals. The micro-grating array has the potential to develop for the DMD-based optical switch with multiple channels.

Radio Channel Allocations With Global Optimality and Bounded Computational Scale

The radio channel assignment (RCA) in wireless networks is an optimization problem that is often found NP-complete. For networks of practical sizes, various heuristic algorithms are used to solve it. However, there are two major issues: finding a globally optimized solution without relying on specific interference models and estimating the computational complexity of general heuristic algorithms. In this paper, we propose a new simulated annealing (SA)-based RCA (SRCA) algorithm to find the globally optimized channel assignment in a distributed way but with bounded computational complexity. We propose using effective channel utilization (ECU) as the evaluation vector, whereas the objective function is to maximize the total ECU in a neighborhood. The ECU can be easily calculated by an access point (AP). The impact of interference is included in the ECU. We propose a hybrid method for estimating the algorithm's computational scale (CS), i.e., the number of channel reallocations until the network reaches a convergence state, by combining analytical and experimental methods. The resulting algorithm is a dynamic and distributed algorithm. Our extensive simulation results have demonstrated that it quickly achieves 99% of the global maximum with a chance over 95%, whereas its complexity is linear with the number of routers in the network.

지상파 DMB 채널 재배치 방안에 따른 송수신환경 변화 분석

Abstract Many communications and broadcast media have emerged by the rapid development of wireless communication and broadcasting technologies, so the radio resources are insufficient for these services. DMB can use the regional integrated channel due to the SFN broadcasting network, so DMB uses the frequency efficiently. However, the domestic DMB uses the existing analog TV frequency band and uses a plurality of channels in some areas because of the interference with the analog TV. However, the broadcasting of the analog TV was terminated, so the channel reallocation of the terrestial DMB is necessary for the efficient use of frequencies. This paper proposes the channel reallocation method of the terrestial DMB and analyzes the change of transmission and reception environments by using simulations. Key Words : Terrestial DMB, Channel reallocation, SFN, Interference analysis * 준회원, 충북대학교 전파통신공학과 ** 정회원, 충북대학교 전파통신공학과, 교신저자접수일자 2013년 11월 28일, 수정완료 2013년 12월 11일게재확정일자 2013년 12월 13일Received: 28 November, 2013 / Revised: 11 December, 2013 Accepted: 13 December, 2013

Channels Reallocation In Cognitive Radio Networks Based On DNA Sequence Alignment

Nowadays, It has been shown that spectrum scarcity increased due to tremendous growth of new players in wireless base system by the evolution of the radio communication. Resent survey found that there are many areas of the radio spectrum that are occupied by authorized user/primary user (PU), which are not fully utilized. Cognitive radios (CR) prove to next generation wireless communication system that proposed as a way to reuse this under-utilised spectrum in an opportunistic and non-interfering basis. A CR is a self-directed entity in a wireless communications environment that senses its environment, tracks changes, and reacts upon its findings and frequently exchanges information with the networks for secondary user (SU). However, CR facing collision problem with tracks changes i.e. reallocating of other empty channels for SU while PU arrives. In this paper, channels reallocation technique based on DNA sequence alignment algorithm for CR networks has been proposed.

상향링크 셀룰러 시스템에서 그룹 탐색 기반의 분산동적채널할당 방법

주파수 재사용률 1을 사용하는 상향링크 셀룰러 시스템의 동적채널할당 (DCA : Dynamic Channel Allocation) 방법에서는 신규호가 채널 할당을 요구할 때 신규호의 SINR (Signal to Interference and Noise Ratio)이 요구된 SINR 보다 작거나 할당할 채널이 부족한 경우에 신규호 차단이 발생한다. 이러한 차단된 신규호에 대한 추가적인 채널할당을 위하여 인접한 셀에서 채널을 가져오게 된다. 이 경우에 동일 채널 간섭 (CCI: Co-Channel Interference)이 발생하게 되고 이로 인해 기존 호의 SINR이 저하되어 기존 호에 대한 채널 재할당을 해야 하는 경우가 생기게 된다. 따라서 신규호 블록율이 증가할수록 인접한 셀에서 채널을 가져오는 경우의 수를 증가시킴으로써 채널 재할당 과정은 복잡한 연산과정이 필요한 NP-hard 문제가 된다. 그 문제를 해결하기 위하여 본 논문에서는 차단된 신규호를 감소시킴으로써 추가적인 채널할당을 위하여 인접한 셀에서 채널을 가져오는 횟수를 감소시키고 그 결과로 채널 재할당 횟수가 감소되어 복잡한 연산과정을 피할 수 있는 Group Search-based DCA 방법을 제안한다. 제안한 방법은 신규호의 차단율을 감소시키기 위하여 신규호에 대한 채널할당시 단말이 속해 있는 셀뿐만 아니라 그 주변의 셀까지를 한 그룹으로 묶어서 채널 탐색 범위를 확장하는 방법을 사용한다. 시뮬레이션 결과에서 제안한 Group Search-based DCA가 탐색 범위를 단말이 속한 셀로 한정하는 Single Search-based DCA보다 신규호 차단률과 시스템 수율 성능을 향상시킴을 확인할 수 있었다. In DCA (Dynamic Channel Allocation) scheme of uplink cellular system appling a frequency reuse factor of one, when a new call requests a channel, the new call will be blocked if its SINR (Carrier to Noise and Interference Ratio) is less than the required SINR or there is no available channel. The additional channel allocation for the blocked new call can be performed with channel borrowing in the adjacent cells. The channel borrowing causes the CCI (Co-Channel Interference), thus the SINR of the existing calls is deteriorated and the channel reallocation for the existing calls is required. As a result, the channel borrowing leads to a complex calculation so that it is a NP-hard problem. Therefore, to overcome the problem, we propose a novel Group Search-based DCA scheme which decreases the number of the blocked new calls and then reduces the number of the channel reallocation by the channel borrowing for the blocked new calls. The proposed scheme searches the all channels in a group of the adjacent cells and home cell at the same time in order to minimizes the number of the blocked new calls. The simulation results show that proposed Group Search-based DCA scheme provides better new call blocking probability and system throughput than the existing Single Search-based DCA scheme which searches only the channels in home cell.

Cell Edge Capacity Improvement by Using Adaptive Base Station Cooperation in Cellular Networks with Fractional Frequency Reuse

The present paper focuses on the application of the base station cooperation (BSC) technique in fractional frequency reuse (FFR) networks. Fractional frequency reuse is considered to be a promising scheme for avoiding the inter-cell interference problem in OFDMA cellular systems, such as WiMAX, in which the edge mobile stations (MSs) of adjacent cells use different subchannels for separate transmission. However, the problem of FFR is that the cell edge spectral efficiency (SE) is much lower than that of the cell center. The BSC technique, in which adjacent BSs perform cooperative transmission for one cell edge MS with the same channel, may improve the cell edge SE. However, since more BSs transmit signals for one cell edge MS, the use of BSC can also increase the inter-cell interference, which might degrade the network performance. In this paper, with a focus on this tradeoff, we propose an adaptive BSC scheme in which BSC is only performed for the cell edge MSs that can achieve a significant capacity increase with only a slight increase in inter-cell interference. Moreover, a channel reallocation scheme is proposed in order to further improve the performance of the adaptive BSC scheme. The simulation results reveal that, compared to the conventional FFR scheme, the proposed schemes are effective for improving the performance of FFR networks.

Broadcast to Broadband: Unlicensed Access to Unused TV Channels?

Although much public attention has focused on the US digital TV transition- and the resulting reallocation of analog TV channels by auction to wireless carriers - the US Federal Communications Commission will decide how to reallocate an even larger swath of prime TV band spectrum this year: the unused "white space" between occupied DTV channels. This reallocation of unused spectrum from broadcasting to broadband permits unlicensed access for both fixed and mobile applications. Although this policy is strongly supported by high-tech companies and consumer advocates, it's just as strongly opposed by broadcast licensees and other incumbent users of the TV band.