Joydev Ghosh

Mitigating ICI at cell edges in cognitive-femtocell networks through fractional frequency reuse

In this paper, we consider a situation where femtocells are deployed over the existing macrocell network and share the same frequency spectrum with macrocells where we focus only on downlink situation. It is essential to implant femtocell at cell edges due to the fact that the number of outage user is large because of their position which is far away from macrocell base station MBS located at macrocell centre, more precisely at 0, 0 coordinates. In general, the uncoordinated deployment of femtocell creates the potential for severe interference to co-located femtocells, especially in dense deployment, resulting in large inter cell interference ICI effect on the users located at cell edges. Here, we propose dynamic FFR algorithm at cell edges to overcome all possible difficulties in the networks. Frequency reuse is an approach to increase the signal to interference plus noise ratio SINR and channel capacity Bits/s/Hz. The bit error rate BER is also evaluated by maximal ratio combining MRC diversity technique for accurate transmission over multipath fading dispersive channels. The simulation results conclusively validate the superior performance of the network model in interference mitigation, precisely in high density FAP scenarios.

The Implications of Cognitive Femtocell Based Spectrum Allocation Over Macrocell Networks

We propose an analytical framework of significant influence of deployment of femto base stations (FBSs) in a dual-tier network constituted of macro base stations (MBSs). As because of uncoordinated deployment, FBSs results in destructive interference to MBSs and vice versa. But, throughput efficiency of indoor (femtocell) and outdoor (macrocell) environment substantially increases due to an optimum reutilization of available spectrum. The quality of service is further getting optimized in terms of throughput and network coverage because of incorporation of steerable beamforming. Finally, the effectiveness of the scheme is verified by extensive matlab simulation.

Secondary Network Throughput Analysis Applying SFR in OFDMA-CR Networks

In OFDMA femtocell networks, the licensed spectrum of the macro users (MUs) are available to the femto users (FUs), on the condition that they do not spark off notable interference to the MUs. We contemplate wireless data for femto user (FU)/secondary user (SU) in cognitive radio (CR) networks where the frame structure split up into sensing and data transmission slots. Moreover, we consider soft frequency reuse (SFR) technique to improve secondary network throughput by increasing the macrocell edge user power control factor. SFR applies a frequency reuse factor (FRF) of 1 to the terminal located at the cell centre for that all base stations (BSs) share the total spectrum. But for the transmission on each subcarrier the BSs are confined to a certain power level. However, more than 1 FRF uses for the terminals near to the macrocell edge area. In this context, we conceptualize the cognitive femtocell in the uplink in which the femtocell access point (FAP) initially perceive by sensing to find out the availability of MU after that FAP revamps its action correspondingly. Appropriately, when the MU is sensed to be nonexistent, the FU transmits at maximum power. In other respect, the FAP make the best use of the transmit power of the FU to optimize the secondary network throughput concern to outage limitation of the MU. Finally, effectiveness of the scheme is verified by the extensive MATLAB simulation.

An analytical model of sequential hypothesis estimation for femtocell network optimisation

ABSTRACT Femto Base Stations (FBSs) are small cells that provide radio coverage for low-power-consuming smart mobile devices in indoors. In this article, we contemplate on the networks optimisation issue of a number of FBSs which anticipate joint network coverage in commercial area. In such a situation, FBSs reduce coverage overlapping, network holes and make sure a balanced traffic load is distributed among them. We apply sequential hypothesis estimation methods to quantify the probabilistic accuracy of a provided femtocell (small cell) configuration at runtime. If any disobeying is observed in providing the required standard of quality service, a self-optimisation process is enabled to build on the present configuration.

MAC Protocol Operation in Energy Harvesting for 5G Networks

Two vital challenges arise in the next generation 5G networks: scarcity of spectrum and the aspect of energy efficiency (EE). In this letter, we first formulate the prime issue, i.e., energy harvesting (EV) for 5G wireless networks, in which spectrum and energy resources are efficiently received and resourcefully managed. Thereafter, we introduce a medium access control (MAC) scheme for dual tier 5G networks; it also invokes the simultaneous wireless information and power transfer (SWIPT) technique with other data transmission schemes, i.e., cooperative transmission (CT) scheme and non-cooperative transmission (NCT) scheme with EV abilities. Illustrative results demonstrate significant improvement in aggregated throughput and EE.

Implementing a flexible testbed using dynamic FFR scheme in OFDMA based cognitive radio networks

In this paper, the femtocell resource allocation in the Orthogonal Frequency Division Multiple Access (OFDMA) integrated cognitive radio (CR) networks has been demonstrated to optimize the network performance, while reducing the outage users at cell edges. The sub-band sharing flexibility not only improves the spectral efficiency of the dynamic FFR scheme against conventional approach but also it alleviates outage probability and further noticeable amount of improvement can be found in superior performance parameters such as capacity, CDF of SINR and overall cell throughput. We yield an analytical framework to ascertain the orthogonality of the subcarriers by compensating carrier frequency offset (CFO) to ensure better OFDMA performance in the proposed network model and illustrates the influence of frequency reuse factor (FRF) at cell edges via simulation results.

Network Optimization Using Femtocell Deployment at Macrocell Edge in Cognitive Environment

This research focuses on the problem of cell edge user’s coverage in the context of femtocell networks operating within the locality of macrocell border where pathloss, shadowing, Rayleigh fading have been included into the environment. As macro cell edge users are located far-away from the macro base station (MBS), so that, the underprivileged users (cell edge users) get assisted by the cognitive-femto base station (FBS) to provide consistent quality of service (QoS). Considering various environment factors such as wall structure, number of walls, distance between MBS and users, interference effect (i.e., co-tier and cross-tier), we compute downlink (DL) throughput of femto user (FU) for single input single output (SISO) system over a particular sub-channel, but also based on spectrum allocation and power adaptation, performance of two tier network is analyzed considering network coverage as the performance metric. Finally, the effectiveness of the scheme is verified by extensive matlab simulation.

Functionality analysis of centralized CR network with integrated femtocell under the presence of PU

Channel sharing is anticipated to permit several cognitive radio (CR) nodes together use the unutilized spectrum resource for opportunistic transmission. Here, the channel sharing done by taking into account the transmission range as a three layers assumption. In this paper, a channel sharing scheme is exhibited that accommodates spectrum multifariousness for femtocell integrated centralized CR networks, for the time being the individual users are liable to be mobile. Individual node is uniquely allocated a channel while assuming its channel occupancy time for stationary case which signifies longest interval, the position of the node and the fairness factor in terms of channel access opportunity. Individual of channel sharing metrics contributes to a higher optimization difficulties and the ultimate aim is to maximize the whole utility of the networks. Numerical outcomes from simulation let out significant improvement in average effective capacity by decreasing spectrum handoffs. Finally, the effectiveness of the scheme is verified by extensive matlab simulation.

Performance Improvement of Outage Users at Cell Edges through Cognitive-Femtocell Deployment over Macrocell Network

This research focuses on the problem of cell edge user coverage in the context of femtocell networks operating within the locality of macro cell border. The macro cell-edge users get assisted by the cognitive-femto base station (FBS) to receive a consistent quality of service (QoS) because of their long distance from the macro base station (MBS). Considering various environment factors such as wall structure, number of walls, distance between macro cell and users, interference effect (i.e., cotier and cross-tier), we compute not only the overall outage probability of single input single output (SISO) system and single input multiple output (SIMO) system users but also based on sub carrier and power allocation the performance of the two tier network is analysed with macro cell throughput as the performance metric. Finally, the effectiveness of the scheme is verified by extensive matlab simulation.