Hashim Safdar

Voronoi cell geometry based dynamic Fractional Frequency Reuse for OFDMA cellular networks

Interference Management (IM) is one of the major challenges of next generation wireless communication. Fractional Frequency Reuse (FFR) has been acknowledged as an efficient IM technique, which offers significant capacity enhancement and improve cell edge coverage with low complexity. In literature, FFR has been analyzed mostly with cellular networks described by Hexagon Grid Model, which is neither tractable nor scalable to the dense deployment of next generation wireless networks. Moreover, the perfect geometry based grid model tends to overestimate the system performance and not able to reflect the reality. In this paper, we use the stochastic geometry approach, FFR is analyzed with cellular network modeled by homogeneous Poisson Point Process (PPP). A dynamic frequency allocation scheme is proposed which take into account the randomness of the cell coverage area describe by Voronoi tessellation. It is shown that the proposed scheme outperforms the traditional fixed frequency allocation schemes in terms of per user capacity and capacity density.

Resource allocation for uplink M2M communication: A game theory approach

Machine-to-Machine (M2M) communication in cellular network is the driver for the future Internet of Things (IoT). The main challenge of M2M communication is the possibility of huge traffic in the uplink network that can cause problem in the network. This paper considers the problem of resource allocation among machines connecting in uplink to different femto base stations (FBSs). Resource allocation problem is analyzed through both non-cooperative and cooperative game to maximize their data rate and minimize utilization of power. Numerical result shows that by adapting non-cooperative game, all machines are getting data rate as per Nash Equilibrium (NE) or either they can set their strategy to maximize their data rate selfishly. On the other hand for coalitional game theory approach machines who participate in game are getting fair resource allocations.

Interference management for irregular cell geometry heterogeneous networks

Recent trends of bandwidth hungry application services in cellular communication put tremendous pressure on the network operators to significantly increase the system capacity. Within such perspective, the deployment of femtocells offers reliable and cost effective means to enhance the system capacity and indoor coverage. However, the random deployment of femtocells challenges several technical aspects of the existing cellular systems. The most obvious challenge is the occurrence of interference, which is more severe if spectrum management is not carefully considered. Fractional Frequency Reuse (FFR) has emerged as an attractive interference management technique due to its low complexity and significant coverage improvement. However, most of the previous work analyzes the performance of FFR for perfect geometry based models, whereas no practical deployment has such symmetry. In this paper we investigate the performance of FFR for cellular network based on irregular cell geometry. Furthermore, a novel FFR scheme is proposed for two-tier (macro-femto) network and the capacity of the system is evaluated. It is shown that the proposed scheme outperform the conventional frequency allocation schemes in term of capacity and cell edge performance.

Resource allocation for uplink M2M communication in multi-tier network

Machine-to-Machine (M2M) communication in heterogeneous cellular networks (HCNs) is “ONE OF THE DRIVERS” for the future Internet of Things (IoT). Coverage areas of HCNs cells may vary and the capabilities to handle users may vary also. To support massive numbers of machines connected in uplink in HCNs, one of the challenging issues of M2M communication is the possibility of huge traffic that can cause overload problem for specific tier/tiers. Increase the capacity of the network and avoid overload condition for BSs, machines will need to be pushed to the less loaded BSs even they offered a lower instantaneous SINR than the nearest BS. To push the machine to less loaded BS, biasing is introduced to enhance the coverage of the machine or group of machines. This paper proposes the solution of resource allocation in uplink by using cooperative game theory approach by introducing a biasing factor to enhance the overall system performance with fair utilization of radio resources.

Middleware framework for network virtualization in SHAAL

Wireless Sensor Network (WSN) has led to a new paradigm of Internet of Things (IoT). WSNs are usually deployed for a particular application. However, the demand of WSNs in Smart Home and Ambient Assisted Living (SHAAL) is the accumulation and allocation of multiple resources providing diverse services and applications. Virtualization of a sensor network is an emerging technique that permits aggregation of several independent heterogeneous sensor networks. The technique of virtualization poses overhead challenges like more processing and power consumption. In this paper efforts have been put forward by proposing an energy aware middleware framework that resides on the sensor nodes to achieve network virtualization for SHAAL.

Multi-thread based middleware for sensor network virtualization

Wireless Sensor Network (WSN) has led to a new paradigm of Internet of Everything (IoE). In case of Ambient Assisted Living (AAL) that is based on the sensor network is usually deployed for single application. However, the future of WSNs based on sensors lies in the multiple application support and the aggregation of resources either in the form of hardware or software. To deal with the challenges of aggregation of sensors in the health care environment, virtualization of a sensor network is an evolving concept that enables aggregation of multiple independent heterogeneous sensor networks under one roof. In order to virtualize the sensors and networks, middleware layer role is the most dominant one. Furthermore, middleware for sensors poses the overhead challenges like processing time, memory utilization, sampling rate, delay, and power consumption. In this paper efforts have been put forward by proposing a middleware framework for sensor network that uses multi-threading technique that increases the sampling frequency and reduces the delay caused by the hardware abstraction layer that resides on top each sensor node. Mathematical model shows significant improvement in the processing time.

Fractional frequency reuse for irregular geometry based heterogeneous cellular networks

Indoor coverage and capacity are the major limitations of the current cellular systems. In such perspective, femtocells deployment has attracted considerable interest. However, the random and co-channel deployment of femtocells poses severe interference management challenges, especially at the cell edges. Recently, Fractional Frequency Reuse (FFR) has emerged an attractive technique for co-tier and cross-tier interference in multi-tier cellular deployment. However, most of the previous work analyzes the performance of FFR for perfect cell geometry models. Applying regular resource of the standard FFR scheme to the realistic cellular networks with high irregularity in the cell geometry and channel conditions leads to sub-optimal performance. In this paper we investigate the performance of FFR for two-tier cellular network based on irregular cell geometry. To capture the realistic network scenario the position of Macro Base Stations (MBSs) and Femto Base Station (FBSs) are modeled with Hard Core Point Process (HCPP) and Poisson Point Process (PPP) respectively. Furthermore, Sectored-FFR scheme with optimal sub-band allocation is proposed in this paper and the capacity of the system is evaluated. Simulation results show that the proposed Sectored-FFR scheme outperforms the conventional FFR schemes in terms of throughput and capacity.

Distributed resource allocation for spatially distributed irregular cells

It is expected that the number of mobile users will increase rapidly in the coming future for uplink communication. Therefore, the future cellular network should accommodate large number of these mobile users and their resource allocation. The frequency reuse concept being used massively to overcome this resource constraint issue. The massive reuse of frequency creates serious interference problem. To overcome the interference issue from frequency reuse, the fractional frequency reuse concept has introduced for hexagonal/regular cells and recently for irregular cells with sectoring. The problem of resource allocation for the irregular cell edge users is critical due to not fixed cell size and location which dramatically reduce the spectrum efficiency of the system. The proposed scheme provides a new way to analyze the resource allocation by spatially partitioning a cell edge coverage into multiple regions with different dynamic resource distribution for cell edge users. The noncooperative game for subcarrier allocation is considered aiming at maximizing the cell edge users throughput and error free transmission by reducing the impact of interference to and from neighboring cells. This proposed scheme enhances the system performance by reducing improved data rate.

Fractional frequency reuse for irregular cell geometry OFDMA systems

Future cellular systems are targeting aggressive frequency reuse to meet the ever increasing demands for capacity and throughput. However, aggressive frequency reuse results in high inter cell interference (ICI) especially at the cell edges. Fractional Frequency Reuse (FFR) has recently emerged as an attractive interference management approach in OFDMA cellular systems. In literature, FFR is studied mostly for regular cell geometry models and very limited work exists for irregular cell geometry models. In this paper we investigate the performance of FFR for cellular network based on irregular cell geometry. Furthermore, full frequency reuse is achieved by sectoring the cell edge users. Applying regular sub-bands of equal size to the irregular sectors of the cell-edge region leads to suboptimal performance. Therefore, a low complexity FFR scheme with optimal sub-carrier allocation is proposed for multicellular network and the capacity of the system is evaluated. It is shown that the proposed FFR scheme outperform the conventional frequency allocation schemes in term of cell edge throughput.