Non-uniform Traffic Conditions Research Articles

Heuristic Radio Resource Management for Massive MIMO in Satellite Broadband Communication Networks

The advent of technologies allowing the implementation of flexible satellite payloads is opening up great opportunities to efficiently cope with non-uniform traffic conditions. The latter is one of the “crux” of modern satellite broadband access service economic provision. In this paper we derive affordable (linear) complexity radio resource management (RRM) techniques for satellite multi-beam broadband communication networks that are closely approaching the optimum solution which has an exponential complexity with the number of users. The proposed heuristic RRM solution is applied to the most demanding Massive Multiple Input Multiple Output (M-MIMO) case. It is shown that the low-complexity payload pragmatic M-MIMO solution combined with heuristic RRM is able to efficiently cope with very different traffic conditions with a small penalty in terms of throughput compared to the much more complex ideal Minimum Mean Square Error (MMSE) M-MIMO adopting the same RRM algorithm. Instead, the pragmatic M-MIMO with heuristic RRM is outperforming MMSE M-MIMO exploiting simple RRM.

Low latency Path Aware XY-X Routing Algorithm for NoC Architectures

Route specific information with the SoC needs a great deal of wiring, which increases the Resistance & Capacitance (RC) component of the system. Network on Chip (NoC) is utilized as the interface to address the problems in SoC, On-chip interconnection network in NoC has gained more consideration over steadfast wiring and buses, like lower latency, scalability and high performance. Present routing algorithms in NoC is suffered from load balancing at incarnation networks under non-uniform traffic conditions, causes increase the NoC trade-offs (latency and throughput). Adaptive routing is a technique to progress the load balance, but previous adaptive routing techniques used uniform traffic patterns to form the routing decisions. This paper proposes a new approach at non- uniform traffic patterns in channel state and path specific, Path Aware Routing (PAR XY-X) uses a timeout piggybacking for acknowledgement and load shedding to avoid congestion which choose optimistic path calculation unit to connect the destination node without glue logic decisions in routing. PAR XY-X outperforms the Normal XY routing by 20% and 33% with respect to Avg.latency and throughput.

Reducing Call Blocks in Cellular Network with Non-Uniform Traffic Conditions

Abstract In cellular networks, while the motivation behind all basic channel assignment strategies is the better utilization of the available frequency spectrum with the consequent reduction of the call blocking probability in each cell, very few of them deal with the problem of non-uniform traffic demand in different cells which may lead to a gross imbalance in the system performance. Mobile users in hot cells (the cells with heavy traffic loads) may suffer from low throughput due to the load imbalance problem. In this paper, we propose a cost effective and simple load balancing scheme that can effectively reduce the overall call blocking. A common set of channels are determined dynamically which can be used simultaneously in all the cells. Cell tiers with different radii are used to cope with the interference introduced by using same set of channels simultaneously in all cells. The performance of the proposed scheme is presented in terms of call blocking probability and channel utilization. Simulation results show that the proposed scheme can reduce the call blocking significantly in highly congested cell.

Analytic Models of SSD Write Performance

Solid-state drives (SSDs) update data by writing a new copy, rather than overwriting old data, causing prior copies of the same data to be invalidated . These writes are performed in units of pages , while space is reclaimed in units of multipage erase blocks , necessitating copying of any remaining valid pages in the block before reclamation. The efficiency of this cleaning process greatly affects performance under random workloads; in particular, in SSDs, the write bottleneck is typically internal media throughput, and write amplification due to additional internal copying directly reduces application throughput. We present the first nearly-exact closed-form solution for write amplification under greedy cleaning for uniformly-distributed random traffic, validate its accuracy via simulation, and show that its inaccuracies are negligible for reasonable block sizes and overprovisioning ratios. In addition, we also present the first models which predict performance degradation for both LRW (least-recently-written) cleaning and greedy cleaning under simple nonuniform traffic conditions; simulation results show the first model to be exact and the second to be accurate within 2%. We extend the LRW model to arbitrary combinations of random traffic and demonstrate its use in predicting cleaning performance for real-world workloads. Using these analytic models, we examine the strategy of separating “hot” and “cold” data, showing that for our traffic model, such separation eliminates any loss in performance due to nonuniform traffic. We then show how a system which segregates hot and cold data into different block pools may shift free space between these pools in order to achieve improved performance, and how numeric methods may be used with our model to find the optimum operating point, which approaches a write amplification of 1.0 for increasingly skewed traffic. We examine online methods for achieving this optimal operating point and show a control strategy based on our model which achieves high performance for a number of real-world block traces.

Adaptive Limited Dynamic Bandwidth Allocation Scheme to Improve Bandwidth Sharing Efficiency in Hybrid PON Combining FTTH and Wireless Sensor Networks

This paper proposes a dynamic bandwidth allocation algorithm that improves the network performance and bandwidth sharing efficiency in the upstream channels of a hybrid passive optical network (PON) that combines a fiber-to-the-home (FTTH) access network and wireless sensor networks (WSNs). The algorithm is called the adaptive limited dynamic bandwidth allocation (ALDBA) algorithm. Unlike existing algorithms, the ALDBA algorithm is not limited to controlling just FTTH access networks, it also supports WSNs. For the proposed algorithm, we investigate the difference in the lengths of generated data packets between the FTTH terminals and sensor nodes of WSN to effectively evaluate the end-to-end average packet delay, bandwidth utilization, time jitter, and upstream efficiency. Two variants of the proposed algorithm and a limited service (LS) scheme, which is an existing well-known algorithm, are compared under non-uniform traffic conditions without taking into consideration priority scheduling. We demonstrate the proposed scheme through simulation by generating a realistic network traffic model, called self-similar network traffic. We conducted a detailed simulation using several performance parameters to validate the effectiveness of the proposed scheme. The results of the simulation showed that both ALDBA variants outperformed the existing LS scheme in terms of average packet delay, bandwidth utilization, jitter, and upstream efficiency for both low and high traffic loads.

Scheduling algorithm for VOQ switches

A variety of matching schemes for VOQ switches that provide high throughput for uniform traffic have been proposed. The dual round robin matching (DRRM) scheme has performance similar to iSLIP and lower implementation complexity. DRRM with exhaustive service (EDRRM) algorithm was created as modification of DRRM algorithm with goal to improve performance of DRRM algorithm for bursty and non-uniform traffic conditions. Under extremely unbalanced arrival traffic, an exhaustive service policy may lead to unfairness and starvation. This paper proposes matching scheme for VOQ switches that provides high throughput almost the same as EDRRM scheme and avoid unfairness and starvation under unbalanced traffic.

A dynamic radio resource management technique for multiple APs in WLANs

As more and more wireless LANs are deployed in many popular locations, there is a need for dynamic radio resource management (RRM) schemes. This paper proposes a new dynamic RRM technique for multiple APs network. First, we develop a real-time algorithm to estimate the number of active stations from the standpoint of an AP, instead of a station. Second, we propose a dynamic RRM algorithm that not only significantly increases network performance but also reduces the co-channel interference. Third, we find the optimal switching probability that minimizes the transient time for an AP to reach its equilibrium state. For uniform traffic conditions, our scheme produces classical optimal frequency assignments. For non-uniform traffic conditions, it produces sub-optimal frequency assignments. Our simulations have shown that the proposed RRM technique adapts to dynamic network conditions and increases the channel throughput up to 65% in less than 20 iterations. The results can be applied to practical WLANs to significantly improve network performance

Timeslot-sharing algorithm with a dynamic grouping for WDM broadcast-and-select star networks

The all-to-all transmission schedule is suitable for Wavelength division multiplexing (WDM) broadcast-and-select star networks under uniform traffic patterns. The performance suffers degradation under non-uniform traffic conditions. The timeslot-sharing algorithm with a dynamic grouping is proposed to decrease the degradation under the non-uniform traffic matrices. According to a given traffic matrix, the algorithm decomposes the given traffic matrix into a transmission matrix and a residual matrix. The algorithm aims to obtain a transmission matrix with most entries and to approach a uniform traffic matrix. Also, its complexity is evaluated. In the simulations, the system with the proposed algorithm provides a superior performance based on throughput, packet delay and node’s buffer size. The results show that the algorithm is an efficient solution to improve the performance under uniform and non-uniform traffic distributions.

Performance Analysis of Banyan-Type Multistage Interconnection Networks Under Nonuniform Traffic Pattern

Multistage Interconnection Networks(MINs) have a number of applications in the areas of computer and communications. The most widely researched structure among MIN's is the (1)banyan type network. It has several variations such as buffered banyan, batcher-banyan, tandem banyan, recirculating banyan and banyan with contention resolution phase. Analytical performance evaluation is crucial for justifying the merit of the design in different operational conditions. While several analytical models have been proposed for the performance evaluation of MINs, they are mainly for uniform traffics. Even the models for nonuniform traffics have several shortcomings such as they only consider output buffered structure or do not consider blocking conditions. In this paper, the more accurate models than any other ones so far have been proposed for the performance evaluation of multibuffered banyan-type MIN's under nonuniform traffic condition is obtained. The accuracy of proposed models are conformed by comparing with the results from simulation. Firstly, single buffer model is developed. Markov chain is used for the analysis. Multibuffer model is obtained from single buffer model. Simulation is performed using Discrete Evenet Simulaton(DES) method. As a results, proposed model proves to be very accurate.

Analytical modelling of wormhole-routed k-ary n-cubes in the presence of matrix-transpose traffic

Several analytical models of fully adaptive routing in wormhole-routed k-ary n-cubes under the uniform traffic pattern have recently been proposed in the literature. Although the uniform reference model has been widely used in the past, it is not always true in practice as there are many applications that exhibit non-uniform traffic patterns. There has not been so far any study that describes an analytical model of fully adaptive routing under non-uniform traffic conditions. This paper describes a new analytical model of fully adaptive routing in k-ary n-cubes in the presence of non-uniform traffic generated by matrix-transpose permutations, which is an important communication operation found in many matrix computation problems. Results obtained through simulation experiments confirm that the model predicts message latency with a high degree of accuracy under different working conditions.

A Performance Model of Adaptive Wormhole Routing in k -Ary n -Cubes in the Presence of Digit-Reversal Traffic

Several analytical models of fully adaptive routing in wormhole-routed k-ary n-cubes under the uniform traffic pattern have recently been proposed in the literature. Although the uniform reference model has been widely used by researchers, it is not always true in practice as there are many applications that exhibit traffic nonuniformity. There has hardly been any study that describes an analytical model of fully adaptive routing under nonuniform traffic conditions. This paper describes the first analytical model of fully adaptive routing in k-ary n-cubes in the presence of nonuniform traffic generated by the digit-reversal permutation, which is an important communication operation found in many matrix computation problems. Results obtained through simulation experiments confirm that the model predicts message latency with a good degree of accuracy under different working conditions.

Adaptive cell sectorization for CDMA systems

Given the user distribution in a cell, we investigate the two problems of how to appropriately sectorize the cell such that we minimize the total received power and the total transmit power of all the users, while giving each user acceptable quality of service in both cases. For the received power optimization problem, we show that the optimum arrangement equalizes the number of users in each sector. The transmit power optimization is formulated as a graph partitioning problem that is polynomially solvable. We provide an algorithm that finds the best sectorization assignment as well as the optimal transmit powers for all the users. The computational complexity of the algorithm is polynomial in the number of users and sectors. For both the received power optimization and the transmit power optimization, under nonuniform traffic conditions, we show that the optimum arrangement can be quite different from uniform cell sectorization (equal width sectors). We also formulate and solve the transmit power optimization and cell sectorization problem in a multicell scenario that would improve the capacity of a hot spot in the network. We observe that, with adaptive sectorization, where the sector boundaries are determined in response to users' locations, received and transmit power savings are achieved, and the number of users served by the system (system capacity) is increased compared to uniform sectorization of the cell.

Correction to "Adaptive admission control in wireless multimedia networks under nonuniform traffic conditions"

Correction to "Adaptive admission control in wireless multimedia networks under nonuniform traffic conditions"

NACR: A New Adaptive Channel Reservation in Cellular Communication Systems

Future Personal Communication Networks (PCN) will employ microcells and picocells to support a higher capacity, thus increasing the frequency of handoff calls. Forced call terminations due to handoff call blocking are generally more objectionable than new call blocking. The proposed guard channel schemes for radio channel allocation in cellular networks reduce handoff call blocking probability at the expense of increases in new call blocking probability by giving resource access priority to handoff calls over new calls in call admission control. Under uniform traffic assumptions, it has been shown that a fixed number of guard channels leads to good performance results. In a more realistic system, non-uniform traffic conditions should be considered. In this case, the achieved call blocking probability may deviate significantly from the desired objective. In this paper, we propose a new adaptive guard channel scheme: New Adaptive Channel Reservation (NACR). In NACR, for a given period of time, a given number of channels are guarded in each cell for handoff traffic. An approximate analytical model of NACR is presented. Tabu search method has been implemented in order to optimize the grade of service. Discrete event simulations of NACR were run. The effectiveness of the proposed method is emphasized on a complex configuration.

Adaptive admission control in wireless multimedia networks under non-uniform traffic conditions

Adaptive admission control in cellular wireless networks reserves bandwidth for handoff calls, which is proportional to the traffic intensity in the surrounding cells. This paper analyzes performance (QoS) of the adaptive admission algorithm in the presence of nonuniform traffic conditions in the network. We model the performance of small, moderate, and large hot-spots, and analyze average cell capacity utilizations and their derivatives when the hot-spot new call arrival rate is growing and surrounding cells operate at the constant load. The analysis shows that under sufficient bandwidth reservation, derivatives of the hot-spot cell capacity utilizations converge to zero for hot-spot call arrival rates larger than twice the nominal load. Since the average utilization is the linear combination of all the state probabilities of the Markov chain, the convergence of its derivative to zero under high offered loads means that the derivatives of other linear combinations of state probabilities, such as handoff dropping probability and new call blocking probability, will also converge to zero. Therefore, handoff dropping probability and new call blocking probability must be bounded by the logarithmic function of new call arrival rate for large arrival rates. Due to the feedback property embedded in the bandwidth reservation process, our admission algorithm offers QoS bounds both under nominal load and under high arrival rates. The analytical results have been validated by simulations.

Borrowing channel assignment strategies based on heuristic techniques for cellular systems

The demand for more efficient and fast channel allocation techniques in cellular systems increases day by day. Borrowing channel assignment (BCA) was introduced in the literature as a compromise between the classic fixed and dynamic channel allocation schemes. This paper examines the behavior of three heuristic BCA techniques based alternatively on a Hopfield neural network, an efficient evolutionary algorithm named combinatorial evolution strategy (CES) and a third heuristic which combines the basic advantages of the two above computational intelligence methods. By considering some specific assumptions that follows an ideal cellular mobile model, BCA is formulated as a combinatorial optimization problem. The above heuristics have been extensively applied to solve efficiently such problems in the past. Simulation results, derived for uniform and nonuniform traffic load conditions, are used to compare these BCA schemes each other as also with other well-established allocation techniques.

MA-WATM: a new approach towards an adaptive wireless ATM network

In a cellular multimedia network like wireless ATM (WATM), self control seems primordial. Our new approach is based on the application of DAI (distributed artificial intelligence) techniques in order to build a self-adaptive network within random non-uniform traffic conditions. Attempting to achieve a high network capacity in terms of resource allocation and air interface BER (bit error rate), we propose to apply intelligent agent features to enhance the architecture of WATM systems. In fact, the intelligent platform MA-WATM (multi-agent wireless ATM) is used to provide a flexible integration of the multi-agent technique in wireless entities, BSs (base stations), MSs (mobile stations) and MSCs (mobile switching centers). Two applications are investigated and explored by simulations in order to bear out the feasibility of the multi-agent approach.

Comparison of two novel heuristic dynamic channel allocation techniques in cellular systems

Dynamic channel assignment (DCA) has been discussed in the literature as a way to achieve improved resource management in cellular networks. In the simplest dynamic allocation scheme, all channels are kept in a central pool and are used on a call-by-call basis. DCA is therefore a complex real time operation and various heuristic methods have been devised as mechanisms to give a fast and reliable solution to this problem. This paper examines the implementation of a DCA model using two approaches from the field of evolutionary computation. The first is the so called genetic algorithm (GA) and the second is the combinatorial evolution strategy (CES). Computer simulations evaluate and compare these proposed heuristic DCA schemes concerning their application to a cellular model for both uniform and non-uniform traffic load conditions. © 1998 John Wiley & Sons, Ltd.

Short-term forecasting of traffic delays in highway construction zones using on-line approximators

Highway construction zones are often the cause of traffic delays. This is a natural consequence of the high congestion and nonuniform traffic flow conditions in construction zones. Most of the current algorithms for computing traffic delays are accurate for low density traffic conditions, and address the estimation of current travel time only. This paper presents a method for short-term forecasting of traffic delays in highway construction zones using data from presence detectors. The method is based on a modular approach wherein data from adjacent detectors is processed for estimating the travel time between the two detectors. The travel time estimates are then considered as time-series data, and the problem of short-term forecasting of traffic delay is formulated as a time-series evolution problem. A generic structure referred to as an on-line approximator is used for the prediction of travel time based on current and past travel time estimates. Simulation examples are used to illustrate the traffic delay forecasting algorithm.

The helical switch: a multipath ATM switch which preserves cell sequence

The paper presents a new cell switching architecture for ATM-based networks. The proposed helical switch is a multistage interconnection network which implements the self-routing technique with efficient buffer sharing. Although the switch may route cells along multiple paths, the connection-oriented mode required by the ATM-based network is supported. Cell sequence integrity is guaranteed by introducing a virtual helix which forces cells routed along different paths to proceed in order and fill the internal buffers uniformly. The performance of the helical switch is investigated under uniform and nonuniform traffic patterns. Unlike single-path multistage networks such as buffered banyan networks which can degrade significantly under nonuniform traffic, the helical switch is shown to be quite robust with respect to nonuniform traffic conditions. >