ABSTRACT In this paper, we investigate uplink resource allocation for wireless local area network... more ABSTRACT In this paper, we investigate uplink resource allocation for wireless local area network and cellular network interworking to provide multi-homing voice and data services. The problem is formulated based on the physical layer and medium access control layer technologies of the two networks to ensure that the resource allocation decisions are feasible and can be executed at the lower layers. Furthermore, to efficiently utilize users' equipment (UEs) battery power, the power distribution among multiple network interfaces of the UEs is included in the problem formulation. The optimal resource allocation problem is a multiple time-scale Markov decision process (MMDP) as the two networks operate at different time-scales and due to voice and data service requirements. We derive decision policies for the upper and the lower levels of the MMDP by decomposing each resource allocation problem over multiple time slots to a set of resource allocation problems for individual time slots and solving the resource allocation problems corresponding to individual time slots using convex optimization techniques. To reduce the time complexity, we further propose a heuristic resource allocation algorithm by deriving the decision policies based on a single system state. The system state consists of average square channel gains for dual variable calculation and instantaneous channel gains for resource allocation based on the calculated dual variables. Simulation results demonstrate the achievable throughput and service quality improvements by employing these two algorithms.
ABSTRACT With the proliferation of connected devices and emerging data-hungry applications, the v... more ABSTRACT With the proliferation of connected devices and emerging data-hungry applications, the volume of mobile data traffic is predicted to have a 1000-fold growth by the year 2020. To address the challenge of this data explosion, industry and academia have initiated research and development of 5G wireless networks, which are envisaged to cater to the massive data traffic volume, while providing ubiquitous connectivity and supporting diverse applications with different quality of service (QoS) requirements. To support the expected massive growth of mobile data, a large number of small cells are expected to be deployed indoors and outdoors, giving rise to heterogeneous networks (HetNets), which are considered to be the key path toward 5G. With such large-scale HetNets, network operators face many serious challenges in terms of operation and management, costeffective small cell deployment, and intercell interference mitigation. To deal with those issues, a cloud based platform is introduced, aiming to simplify the deployment, operation and management, and facilitate round-the-clock optimization of the network, to pave the way for the development of 5G. Two case studies are provided to illustrate the benefits of the cloud based architecture. Finally, the related standardization activities are provided and some research topics essential for a successful development of 5G are discussed.
2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications, 2011
ABSTRACT Inter carrier interference (ICI) is deemed as a critical issue in orthogonal frequency d... more ABSTRACT Inter carrier interference (ICI) is deemed as a critical issue in orthogonal frequency division multiple access (OFDMA) systems. Though ICI caused by Doppler spread is negligible in femtocell systems, frequent reception of signals over misaligned subcarriers will introduce severe ICI. Successive interference cancellation and decision feedback equalizers are some of the techniques proposed to mitigate ICI. However, most of these methods are highly complex, and thus, not suitable for commercial femtocell systems. In this paper, a simple equalization technique to reduce ICI in OFDMA based femtocell networks is proposed. It has been designed particularly considering the femtocell system's operating environment and their limited computational capacity. This technique provides excellent ICI reduction performance for smaller delay spreads of the users.
2013 IEEE Wireless Communications and Networking Conference (WCNC), 2013
ABSTRACT Relaying in femtocell networks is a promising and economically viable option to reduce t... more ABSTRACT Relaying in femtocell networks is a promising and economically viable option to reduce the co-channel interference while improving indoor coverage and the network capacity in the next generation wireless networks. However, efficient relay selection as well as subcarrier and power allocation are critical in such networks when multiple users and multiple relays are considered. In this paper, an optimal resource (relay, subcarrier and power) allocation algorithm for co-channel deployed orthogonal frequency division multiple access (OFDMA) based femtocell systems is proposed. The resource allocation problem is formulated as a joint relay, subcarrier and power allocation problem with the objective of maximizing the sum of the weighted rates of the femtocell system subject to protecting the macrocell network's communications. Due to the non-convex nature of the original resource allocation problem, we obtain an optimal solution for the original problem by solving a relaxed problem via dual decomposition. Simulation results demonstrate that our proposed resource allocation algorithm outperforms the resource allocation algorithms proposed in literature by achieving higher throughput at the expense of a slight increment of the system complexity.
2014 IEEE International Conference on Communications (ICC), 2014
ABSTRACT This paper investigates energy efficient uplink communications for battery-constrained m... more ABSTRACT This paper investigates energy efficient uplink communications for battery-constrained mobile terminals (MTs). We consider a heterogeneous wireless medium where MTs communicate with base stations (BSs) and access points (APs) of different networks with overlapped coverage. Unlike the existing research, we develop a joint bandwidth and power allocation framework that maximizes energy efficiency for a set of MTs, in different service areas, with best effort service and multi-homing capabilities. The problem formulation captures the heterogeneity of the medium, in terms of different service areas, channel conditions, available resources at BSs/APs of different networks, and different available maximum power at the MTs. In addition, the framework is implemented in a decentralized manner which is desirable in a case that different networks are operated by different service providers. Simulation results are presented to demonstrate the performance of the proposed framework.
2013 IEEE International Conference on Communications (ICC), 2013
ABSTRACT Efficiency of the wireless local area network (WLAN)/femtocell interworking system essen... more ABSTRACT Efficiency of the wireless local area network (WLAN)/femtocell interworking system essentially relies on the efficiency of the resource allocation protocol employed in the system. Efficiency of the resource allocation protocol depends on whether it has been designed considering physical layer and medium access control layer technologies of different networks in the interworking system. Therefore, in this paper, we formulate a resource (user, subcarrier, and power) allocation problem for maximizing the sum of weighted rates of the interworking system considering multi-homing capable users and the main features of IEEE 802.11 distributed coordination function (DCF) and orthogonal frequency division multiple access (OFDMA) based femtocell networks. Solving this problem optimally is prohibitively complex as it is a non-convex problem. Thus, the problem is sub-optimally solved by dividing it to two sub-problems. A heuristic algorithm is proposed for user and subcarrier allocation while an optimal and fast converging power allocation algorithm is derived based on dual decomposition and the characteristics of Lagrangian. Simulation results have shown that the proposed resource allocation protocol achieves results close to the optimum.
2011 8th International Symposium on Wireless Communication Systems, 2011
ABSTRACT Co-channel interference (CCI) is a major issue faced by efficient co-channel deployed or... more ABSTRACT Co-channel interference (CCI) is a major issue faced by efficient co-channel deployed orthogonal frequency division multiple access (OFDMA) based two-tier femtocell systems. There are several resource allocation mechanisms proposed, such as, [1]–[4], to address this issue. However, none of these methods have considered employing relays in order to reduce transmit power levels, and hence, reduce CCI with the added advantage of extended coverage. Thus, in this paper, a simple resource allocation mechanism, which maximizes the sum of the weighted rates (SWR), for relay assisted femtocell systems is proposed. Its main advantage is the low complexity achieved by exploiting the characteristics of Lagrangian and utilizing the Newton's method.
—In this paper, energy efficient uplink communications are investigated for battery-constrained m... more —In this paper, energy efficient uplink communications are investigated for battery-constrained mobile terminals (MTs) with service quality requirements and multi-homing capabilities. A heterogeneous wireless medium is considered, where MTs communicate with base stations (BSs) and access points (APs) of different networks with overlapped coverage. Different from the existing works, we develop a quality of service (QoS)-based optimization framework for joint uplink bandwidth and power allocation to maximize energy efficiency for a set of MTs with multi-homing capabilities. The proposed framework is implemented in a decentralized architecture, through coordination among BSs/APs of different networks and MTs, which is a desirable feature when different networks are operated by different service providers. A suboptimal framework is presented with a reduced computational complexity as compared with the optimal framework. Simulation results demonstrate the improved performance of both the optimal and suboptimal frameworks over a state-of-the-art benchmark.
ABSTRACT In this paper, we investigate uplink resource allocation for wireless local area network... more ABSTRACT In this paper, we investigate uplink resource allocation for wireless local area network and cellular network interworking to provide multi-homing voice and data services. The problem is formulated based on the physical layer and medium access control layer technologies of the two networks to ensure that the resource allocation decisions are feasible and can be executed at the lower layers. Furthermore, to efficiently utilize users' equipment (UEs) battery power, the power distribution among multiple network interfaces of the UEs is included in the problem formulation. The optimal resource allocation problem is a multiple time-scale Markov decision process (MMDP) as the two networks operate at different time-scales and due to voice and data service requirements. We derive decision policies for the upper and the lower levels of the MMDP by decomposing each resource allocation problem over multiple time slots to a set of resource allocation problems for individual time slots and solving the resource allocation problems corresponding to individual time slots using convex optimization techniques. To reduce the time complexity, we further propose a heuristic resource allocation algorithm by deriving the decision policies based on a single system state. The system state consists of average square channel gains for dual variable calculation and instantaneous channel gains for resource allocation based on the calculated dual variables. Simulation results demonstrate the achievable throughput and service quality improvements by employing these two algorithms.
ABSTRACT With the proliferation of connected devices and emerging data-hungry applications, the v... more ABSTRACT With the proliferation of connected devices and emerging data-hungry applications, the volume of mobile data traffic is predicted to have a 1000-fold growth by the year 2020. To address the challenge of this data explosion, industry and academia have initiated research and development of 5G wireless networks, which are envisaged to cater to the massive data traffic volume, while providing ubiquitous connectivity and supporting diverse applications with different quality of service (QoS) requirements. To support the expected massive growth of mobile data, a large number of small cells are expected to be deployed indoors and outdoors, giving rise to heterogeneous networks (HetNets), which are considered to be the key path toward 5G. With such large-scale HetNets, network operators face many serious challenges in terms of operation and management, costeffective small cell deployment, and intercell interference mitigation. To deal with those issues, a cloud based platform is introduced, aiming to simplify the deployment, operation and management, and facilitate round-the-clock optimization of the network, to pave the way for the development of 5G. Two case studies are provided to illustrate the benefits of the cloud based architecture. Finally, the related standardization activities are provided and some research topics essential for a successful development of 5G are discussed.
2011 IEEE 22nd International Symposium on Personal, Indoor and Mobile Radio Communications, 2011
ABSTRACT Inter carrier interference (ICI) is deemed as a critical issue in orthogonal frequency d... more ABSTRACT Inter carrier interference (ICI) is deemed as a critical issue in orthogonal frequency division multiple access (OFDMA) systems. Though ICI caused by Doppler spread is negligible in femtocell systems, frequent reception of signals over misaligned subcarriers will introduce severe ICI. Successive interference cancellation and decision feedback equalizers are some of the techniques proposed to mitigate ICI. However, most of these methods are highly complex, and thus, not suitable for commercial femtocell systems. In this paper, a simple equalization technique to reduce ICI in OFDMA based femtocell networks is proposed. It has been designed particularly considering the femtocell system's operating environment and their limited computational capacity. This technique provides excellent ICI reduction performance for smaller delay spreads of the users.
2013 IEEE Wireless Communications and Networking Conference (WCNC), 2013
ABSTRACT Relaying in femtocell networks is a promising and economically viable option to reduce t... more ABSTRACT Relaying in femtocell networks is a promising and economically viable option to reduce the co-channel interference while improving indoor coverage and the network capacity in the next generation wireless networks. However, efficient relay selection as well as subcarrier and power allocation are critical in such networks when multiple users and multiple relays are considered. In this paper, an optimal resource (relay, subcarrier and power) allocation algorithm for co-channel deployed orthogonal frequency division multiple access (OFDMA) based femtocell systems is proposed. The resource allocation problem is formulated as a joint relay, subcarrier and power allocation problem with the objective of maximizing the sum of the weighted rates of the femtocell system subject to protecting the macrocell network's communications. Due to the non-convex nature of the original resource allocation problem, we obtain an optimal solution for the original problem by solving a relaxed problem via dual decomposition. Simulation results demonstrate that our proposed resource allocation algorithm outperforms the resource allocation algorithms proposed in literature by achieving higher throughput at the expense of a slight increment of the system complexity.
2014 IEEE International Conference on Communications (ICC), 2014
ABSTRACT This paper investigates energy efficient uplink communications for battery-constrained m... more ABSTRACT This paper investigates energy efficient uplink communications for battery-constrained mobile terminals (MTs). We consider a heterogeneous wireless medium where MTs communicate with base stations (BSs) and access points (APs) of different networks with overlapped coverage. Unlike the existing research, we develop a joint bandwidth and power allocation framework that maximizes energy efficiency for a set of MTs, in different service areas, with best effort service and multi-homing capabilities. The problem formulation captures the heterogeneity of the medium, in terms of different service areas, channel conditions, available resources at BSs/APs of different networks, and different available maximum power at the MTs. In addition, the framework is implemented in a decentralized manner which is desirable in a case that different networks are operated by different service providers. Simulation results are presented to demonstrate the performance of the proposed framework.
2013 IEEE International Conference on Communications (ICC), 2013
ABSTRACT Efficiency of the wireless local area network (WLAN)/femtocell interworking system essen... more ABSTRACT Efficiency of the wireless local area network (WLAN)/femtocell interworking system essentially relies on the efficiency of the resource allocation protocol employed in the system. Efficiency of the resource allocation protocol depends on whether it has been designed considering physical layer and medium access control layer technologies of different networks in the interworking system. Therefore, in this paper, we formulate a resource (user, subcarrier, and power) allocation problem for maximizing the sum of weighted rates of the interworking system considering multi-homing capable users and the main features of IEEE 802.11 distributed coordination function (DCF) and orthogonal frequency division multiple access (OFDMA) based femtocell networks. Solving this problem optimally is prohibitively complex as it is a non-convex problem. Thus, the problem is sub-optimally solved by dividing it to two sub-problems. A heuristic algorithm is proposed for user and subcarrier allocation while an optimal and fast converging power allocation algorithm is derived based on dual decomposition and the characteristics of Lagrangian. Simulation results have shown that the proposed resource allocation protocol achieves results close to the optimum.
2011 8th International Symposium on Wireless Communication Systems, 2011
ABSTRACT Co-channel interference (CCI) is a major issue faced by efficient co-channel deployed or... more ABSTRACT Co-channel interference (CCI) is a major issue faced by efficient co-channel deployed orthogonal frequency division multiple access (OFDMA) based two-tier femtocell systems. There are several resource allocation mechanisms proposed, such as, [1]–[4], to address this issue. However, none of these methods have considered employing relays in order to reduce transmit power levels, and hence, reduce CCI with the added advantage of extended coverage. Thus, in this paper, a simple resource allocation mechanism, which maximizes the sum of the weighted rates (SWR), for relay assisted femtocell systems is proposed. Its main advantage is the low complexity achieved by exploiting the characteristics of Lagrangian and utilizing the Newton's method.
—In this paper, energy efficient uplink communications are investigated for battery-constrained m... more —In this paper, energy efficient uplink communications are investigated for battery-constrained mobile terminals (MTs) with service quality requirements and multi-homing capabilities. A heterogeneous wireless medium is considered, where MTs communicate with base stations (BSs) and access points (APs) of different networks with overlapped coverage. Different from the existing works, we develop a quality of service (QoS)-based optimization framework for joint uplink bandwidth and power allocation to maximize energy efficiency for a set of MTs with multi-homing capabilities. The proposed framework is implemented in a decentralized architecture, through coordination among BSs/APs of different networks and MTs, which is a desirable feature when different networks are operated by different service providers. A suboptimal framework is presented with a reduced computational complexity as compared with the optimal framework. Simulation results demonstrate the improved performance of both the optimal and suboptimal frameworks over a state-of-the-art benchmark.
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Papers by Amila Gamage