An analytical approach is developed to evaluate the performance of a hybrid base station (BS) location model which considers the location regularity of macro BSs and topological randomness of small BSs, where the coverage probability and spectral efficiency are derived and verified by simulation. When both tiers have the same BS intensity, the tier of tessellated macro BSs achieves a 50% advantage in spectral efficiency and the tier of underlaid randomly positioned small BSs exhibits a 30% improvement, over that of a 2-tier pure random model where both tiers are modeled by Poisson point processes. With the increasing small BSs to macro BS intensity, the spectral efficiency gain of the hybrid model over that of the pure random model decreases and even becomes marginal, thus providing a design guideline on the small BSs to macro BS intensity ratio to achieve a desired coverage probability and spectral efficiency in HCNs.

In cloud gaming systems, the game program runs at servers in the cloud, while clients access game services by sending input events to the servers and receiving game scenes via video streaming. In this paradigm, servers are responsible for all performance-intensive operations, and thus suffer from poor scalability. An alternative paradigm is called graphics streaming, in which graphics commands and data are offloaded to the clients for local rendering, thereby mitigating the server's burden and allowing more concurrent game sessions. Unfortunately, this approach is bandwidth-consuming, due to large amounts of graphic commands and geometry data. In this paper, we present LiveRender, an open-source gaming system that remedies the problem by implementing a suite of bandwidth optimization techniques including intraframe compression, interframe compression, and caching, establishing what we call compressed graphics streaming. Experiments results show that the new approach is able to reduce bandwidth consumption by 52%-73% compared to raw graphics streaming, with no perceptible difference in video quality and reduced response delay. Compared to the video streaming approach, LiveRender achieves a traffic reduction of 40%-90% with even improved video quality and substantially smaller response delay, while enabling higher concurrency at the server.

This paper analyzes the location-dependent performance metrics of coverage probability and spectral efficiency in hexagonal cellular networks under Rayleigh fading with a general distribution for shadowing and also including two special cases of no shadowing and lognormal shadowing. The effects of system parameters such as frequency reuse factor, transmission probability of base stations, and signal-to-interference-plus-noise ratio gap from Shannon capacity are accurately characterized. The proposed approach is applied to fractional frequency reuse FFR scheme where the impact of FFR on spectral efficiency is evaluated. Numerical results show that i in a lognormal-shadowed Rayleigh fading channel with the shadowing standard deviation of 12dB, the cell area wide spectral efficiency is degraded by approximately 40% compared with when there is Rayleigh fading without shadowing; ii the improvement in spectral efficiency achieved by FFR over the universal frequency reuse increases as the transmission probability increases and the shadowing becomes less severe; and iii in Rayleigh fading without shadowing environment where all the base stations are actively transmitting, FFR achieves approximately 20% improvement in spectral efficiency in the cell edge area. Interestingly, this improvement increases to about 30% if a 3-dB signal-to-interference-plus-noise ratio gap from Shannon capacity is further accounted. Copyright © 2015 JohnWiley & Sons

This paper analyzes downlink coverage probability and spectral efficiency of Poisson cellular networks with lognormal shadowed Rayleigh fading, provided each user is associated to the closest base station (BS). Both location-dependent and cell area wide aspects of the coverage probability and spectral efficiency metrics are presented. Performance impact of system parameters such as frequency reuse factor, transmission probability, and Signal to Interference Ratio (SIR) gap from Shannon capacity are characterized. Numerical results support the view that shadowing significantly degrades the performance. The cell area wide spectral efficiency decreases by 37% when the shadowing standard deviation increases from 0dB to 12dB. Finally, the derived results on location-dependent metrics are applied to Fractional Frequency Reuse (FFR) optimal partitioning in terms of system spectral efficiency, which is found dependent on system parameters such as SIR gap from Shannon capacity. It is also numerically shown that the FFR significantly improves the (link) spectral efficiency for cell edge users. For a user far away from its associated BS (at a distance 3 times the radius of average cell area) and considering SIR gap from Shannon capacity of 3dB, FFR(1,3) improves the (link) spectral efficiency by 239% compared to the universal reuse factor.

In cloud gaming systems, the game program runs at servers in the cloud, while clients access game services by sending input events to the servers and receiving game scenes via video streaming. In this paradigm, servers are responsible for all performance-intensive operations, and thus suffer from poor scalability. An alternative paradigm is called graphics streaming, in which graphics commands and data are offloaded to the clients for local rendering, thereby mitigating the server's burden and allowing more concurrent game sessions. Unfortunately, this approach is bandwidth consuming, due to large amounts of graphic commands and geometry data. In this paper, we present LiveRender, an open source gaming system that remedies the problem by implementing a suite of bandwidth optimization techniques including intra-frame compression, inter-frame compression, and caching, establishing what we call compressed graphics streaming. Experiments results show that the new approach is able to reduce bandwidth consumption by 52-73% compared to raw graphics streaming, with no perceptible difference in video quality and reduced response delay. Compared with the video streaming approach, LiveRender achieves a traffic reduction of 40-90% with even improved video quality and substantially smaller response delay, while enabling higher concurrency at the server.

This paper deals with the performance analysis for the downlink with Rayleigh fading in Orthogonal Frequency-Division Multiple Access (OFDMA)-based hexagonal cellular networks with static frequency reuse. A statistical analytical framework is developed where inter-cell interference is approximated as being generated by surrogate interfering base stations whose locations are modeled by a spatial Poisson point process and the theory of stochastic geometry is exploited. Analytical expressions for coverage probability and spectral efficiency (including location-dependent and cell area wide) are derived and their numerical results are verified by simulation. In addition to the analytical tractability of the proposed framework, the effect of important parameters such as transmission probability, path loss exponent, and SINR gap from Shannon capacity are captured.

The performance of preamble detection in Physical Random Access Channel (PRACH) for long term evolution (LTE) and its advanced degrades when channels become more time dispersive, such as Extended Typical Urban (ETU). However, the Base Station (BS) target received power is determined by users with time dispersive channels, in order to keep the acceptable performance for most of users in a cell. Motivated by the idea of collecting the energy of multiple paths, the optimal statistic is derived in this paper given the Power Delay Profile (PDP) of Rayleigh fading channels. An analytical framework of performance is also proposed in this paper and verified by simulation. It is shown that the proposed optimal statistic increasingly outperforms the traditional peak detecting when time-dispersion of channels increases. Considering the difficulty of achieving the accurate PDP in some scenarios, a suboptimal but robust solution is further developed. Compared with peak detecting, the suboptimal solution lowers the BS's target received power by over 1.1dB for Format 0 PRACH with both 2 and 4 receive antennas in the ETU channel, significantly reduces the user's power consumption and improves the LTE PRACH coverage.

This paper studies the performance of random access backoff algorithm in Long Term Evolution (LTE) system, taking the physical loss into account. Analytical results are developed for system performance metrics including throughout, drop probability and medium access delay. All these analytical results are verified with simulation. Performance of the backoff algorithm under different parameter settings is compared in a typical scenario of LTE. The performance results provide useful insights on optimal backoff parameter settings. For example, under a physical loss probability of 1%, the optimal backoff window size should be set to 1 and the attempt limit set to 2 or 3.