Alvin Ting

Dynamic backhaul sensitive Network Selection Scheme in LTE-WiFi wireless HetNet

Small-cell deployment within a wireless Heterogeneous Network (HetNet) presents backhauling challenges that differ from those of conventional macro-cells. Due to the lack of availability of fixed-lined backhaul at desired locations and due to cost saving reasons, operators may deploy a variety of backhaul technologies in a given network, combining available technologies such as fiber, xDSL, wireless backhaul and multi-hop mesh networks to backhaul small-cells. As a consequence, small-cells capacity may be non-uniform in the HetNet. Furthermore, some small-cells backhaul capacity may fluctuate if wireless backhaul is chosen. With such concerns in mind, a new network selection strategy considering small-cell backhaul capacity is proposed to ensure that users enjoy the best possible user experience especially in terms of connection throughput and fairness. The study compares performance of several common Network Selection Schemes (NSSs) such as WiFi First (WF) and Physical Data Rate (PDR) with the proposed Dynamic Backhaul Capacity Sensitive (DyBaCS) NSS in LTE-WiFi HetNets. The downlink performance of HetNet is evaluated in terms of average throughput per user and fairness among users. The effects of varying WiFi backhaul capacity form the focus for the evaluation. Results show that the DyBaCS scheme generally provides superior performance in terms of fairness and average throughput per user across the range of backhaul capacities considered.

Energy efficiency and cell coverage area analysis for macrocell networks

The issues of energy efficiency and environmental protection are becoming critical issues for both fixed and wireless network operators worldwide. For wireless network operators, the challenge generally lies on providing maximum energy efficiency with largest possible coverage area. In this paper we first investigate the parameters affecting energy efficiency and the cell coverage area. We later analyze the relationship between area power consumption and transmission range (cell radius), transmission power, frequency band, shadowing and the path-loss exponent. From the analysis, optimal inter site distance that utilizing minimum area power consumption can be obtained for different percentage requirement of coverage area corresponding to minimum transmit power that achieves this degree of coverage. The optimal inter site distance is determined for macrocell without the impact of shadowing to be equal about 1250 m with minimum area power consumption of 526 W/km2. With the effect of shadowing, the optimal inter site distance and minimum area power consumption are 1050 m and 778.7 W/km2 respectively.

Optimizing energy efficiency in multi-user OFDMA systems with genetic algorithm

Resource allocation in an OFDMA system has been an extremely challenging optimization task. Due to the nature of the problem, this optimization problem can be NP-hard. The majority of existing methods are based on Lagrangian duality, in combination with gradient-based methods. In this paper, we apply genetic algorithm to tune the power allocated to each sub-channel in an OFDMA system. This is done by applying GA in tuning the power allocated for the mth user in the nth channel (pm,n) after solving the resource allocation problem. The first part is a binary optimization problem, whereas the latter part is a continuous optimization problem. In solving the energy-efficient resource allocation problem, the objective is to minimize the transmitted power while fulfilling the transmission rate demand per user. Our simulation results showed that the GA method can obtain global solutions with speedy convergence.

Energy efficiency of LTE macro base station

The growing energy consumption in wireless networks driven by dramatic increases in mobile users and network traffic, are putting mobile operators under immense challenges towards meeting the demands of both cost reduction and environment conservation. The network Energy Efficiency (EE) considers not only energy consumed by the base station (BS), but also the capacity and coverage of the network. In this paper we study the impact of modulation and coding schemes (MCS), bandwidth (BW) size and transmitted power on the energy efficiency of a LTE macro base station. Although it is very much expected that higher transmission power results in lower EE, the difference actually diminishes when cell size increases. At around 1200m it is found that the EE are almost equal for all transmission power considered. On the other hand, EE increases significantly as the BW increases. Similar effect on EE is observed when MCS changes from lower order to higher order scheme. In fact EE becomes more sensitive to MCS change at higher bandwidth.

Design and capacity performance analysis of wireless mesh network

From the network operators point of view, the high CAPEX/OPEX cost resulting from fixed/wired backhaul links can be inhibitive to successful deployment of broadband wireless services. The emerging wireless mesh network (WMN) technology is seen as one of the potential solutions which may reduce wired backhaul dependency through multihop transmission. Despite the advantages, many remain sceptical on WMNs network capacity and scalability performances particularly when the user density is high. This paper provides an insight on the best possible upper-bound capacity performance of WMN, taking into consideration three key design parameters namely 1) Percentage of wired backhaul points per network, 2) Mesh-to-Access Link-Rate Ratio (R) and 3) Number of radio interfaces per mesh node including hybrid radio options. These design options are compared and contrasted with different deployment densities. The results generally show that the higher the number of backhaul points, the higher the effective access capacity available to each user domain. Increasing the R and the number of radio per mesh node are two alternative means to push up the effective access capacity per user domain without increasing the number of wired backhaul points. This is most significant in multi radio system where about 80% of saving in backhaul points with R= 3 can be achieved compared to 100% backhauled case. It is also found that 50% saving in the number of backhaul points can be achieved with R≥2 for all radio options (except for the pure single radio case) in order to maintain effective access capacity close to full rate (1.0) per user domain.

Capacity and coverage analysis of rural multi-radio multi-hop network deployment using IEEE802.11n radios

This paper presents the capacity and coverage performance analysis of a multiradio multihop network deployment using IEEE802.11n radios for a typical rural area in Malaysia. Insights on the relationships between various key design parameters particularly backhaul link rate, backhaul link distance/multihop distance, coverage size per MAR/total coverage size, number of MIMO spatial multiplex (SM) stream, number of MAR per branch and effective capacity per access point or per user are acquired. Two optimization objectives namely 1) to maximize coverage size and 2) to maximize backhaul distance are introduced.

Energy-aware load adaptive framework for LTE heterogeneous network

One of the main approaches for improving the network energy efficiency EE is through the introduction of load adaptive techniques, where the networks components/subsystems are switched off when the network is lightly loaded. Optimising such a dynamic operation in a heterogeneous network HetNet remains an active topic of research. In this paper, a traffic load-adaptive model that aims to evaluate the EE of base stations in Long Term Evolution LTE HetNet is presented. First, a model that simulates the load-adaptive power consumption behaviour of LTE HetNet is developed. In this regard, a load adaptation factor is introduced to assess the networks EE performance. The model also adapts and predicts the achievable data rate of each base station with respect to the traffic load. Our study shows that the fully load-adaptive LTE HetNet can significantly improve networks EE up to 10%, 40%, and 80% for high, medium, and low loads, respectively, as compared to the conventional non load-adaptive HetNet. In addition, we show that the full adaptive network operation can achieve significant EE gains under a realistic daily traffic profile up to 86%. The proposed evaluation model is essential to assess the network EE and can be used in future studies that focus on improving the adaptation level of the already installed network equipments. Copyright ©2014 John Wiley & Sons, Ltd.

User data rate enhancement using heterogeneous LTE-802.11n offloading in urban area

Data offloading is a method to significantly improve network capacity. Offloading of data from macro-cells to pico-cells helps to ease capacity demand in hotspot areas where user distribution is dense and often demanding high bandwidths per user. This study uses a heterogeneous network using combined Long Term Evolution - WiFi IEEE 802.11n coverage to improve the capacity performance of the network. The heterogeneous network uses the offloading mechanism to enhance the per user capacity of the heterogeneous network. The user distribution is non-uniform and the 802.11n Access Points are positioned in areas with high user density. The offloading mechanism is based on a WiFi-First algorithm where users with sufficient Received Signal Strength to hop on to WiFi will be offloaded while the rest of the users will remain on the LTE network. A real digital map of Kuala Lumpur in the geospatial vector data format,. TAB is used for the simulations. The simulation results show that although around 50% of the users are offloaded to WiFi, the LTE network is only relieved 2.75% of the total capacity usage. This may seem small but due to offloading, nearly 100% increase in average capacity in experienced by the remaining LTE users from 0.05 Mbps to 0.09967 Mbps. The offloaded users also experience an increase of 0.876Mbps on average per user.

End-to-end throughput and delay analysis of WiFi multi-hop network with deterministic offered load

In a wireless multi-hop or mesh network, stations which are connected to Mesh Access Point (MAP) lesser hops from the gateway are expected to enjoy higher throughput and lower delay than stations connected to the MAP further hops away. To solve this issue, we introduce a technique to determine network layer queue size limit of ingress radio interfaces in the multi-radio MAPs. The intention is to partially control the transmit probability of forwarded packets during network congestion. End-to-end throughput and delay with four types of queue configurations were measured in an experimental testbed. The results show that a delay variance reduction of 38× between the first hop and the subsequent hops can be achieved using the proposed technique with a minimal drop (<0.05Mbps) in average throughput. (6 pages)

Design and analysis of WiMAX-WiFi multi-tier network

WiMAX-WiFi multi-tier network has emerged as a promising solution for fast delivery of broadband wireless access services. This is particularly true in places where wired infrastructure is not ready or too expensive. The architecture also has the advantage of taking the complementary features of these diverse technologies (from technical and economic viewpoints) to provide capacity and coverage extension. However, such architecture inspires a wide range of complex and interdependent design options covering network formation, number of radio per node, ratio between WiMAX and WiFi nodes, number hops at WiFi multi-hop tier, channel bandwidth, etc. This paper provides some insights on how different possible configurations perform under different operating conditions and user requirements.