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ABSTRACT: Embedding pico/femto base-stations and relay nodes in a macro-cellular network is a promising method for achieving substantial gains in coverage and capacity compared to macro-only networks. These new types of base-stations can operate on the same wireless channel as the macro-cellular network, providing higher spatial reuse via cell splitting. However, these base-stations are deployed in an unplanned manner, can have very different transmit powers, and may not have traffic aggregation among many users. This could potentially result in much higher interference magnitude and variability. Hence, such deployments require the use of innovative cell association and inter-cell interference coordination techniques in order to realize the promised capacity and coverage gains. In this paper, we describe new paradigms for design and operation of such heterogeneous cellular networks. Specifically, we focus on cell splitting, range expansion, semi-static resource negotiation on third-party backhaul connections, and fast dynamic interference management for QoS via over-the-air signaling. Notably, our methodologies and algorithms are simple, lightweight, and incur extremely low overhead. Numerical studies show that they provide large gains over currently used methods for cellular networks.
IEEE Journal on Selected Areas in Communications 01/2011; · 3.41 Impact Factor
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ABSTRACT: Theoretically, MIMO offers significant capacity benefits, but realizing these gains in deployed wireless systems remains a very challenging problem. MIMO has been used in wireless LAN systems with great success. However, due to the hugely varying spatial profiles and velocity patterns of the access terminals, integrating MIMO techniques in a wireless WAN system has been a difficult design problem. This paper introduces the design paradigms of ultra-mobile broadband, which is poised to become the successor of EVDO as the next generation of high speed wireless system. UMB allows the use of MIMO in various forms to suit the deployment scenario, and elicit as much gain as possible.
Communication Systems Software and Middleware and Workshops, 2008. COMSWARE 2008. 3rd International Conference on; 02/2008
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ABSTRACT: In this paper, we investigate link adaptation and incremental redundancy (IR) retransmission schemes over correlated wireless channels. While computer simulations have been used to study the performance of these techniques, a numerically tractable analytical approach is more desirable to analyze generic protocols, and to reveal insights into the performance tradeoffs. An error-recursion approach is developed in this paper to mathematically analyze the throughput, delay, and energy efficiency of rate-adaptation techniques over fading channels with arbitrary correlations between retransmissions. Using Reed-Solomon codes as an example, we quantitatively predict the performance tradeoff of throughput and latency for IR schemes and the performance dependency on the channel correlation. Numerical results also show that reactive rate-adaptation schemes with IR retransmission outperform proactive rate-adaptive schemes, even with perfect channel side information, in terms of throughput and energy efficiency.
IEEE Transactions on Communications 11/2005; · 1.68 Impact Factor
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ABSTRACT: Modified ARQ (automatic-repeat-request) techniques based on turbo
coding are investigated for asynchronous DS-CDMA (direct-sequence
code-division multiple-access) data networks under shadowing and
frequency selective fading channel conditions. The throughput, delay,
and energy efficiency performance of standard ARQ, metric combining, and
RCPT (rate compatible punctured turbo) coded ARQ schemes are compared
via simulations. The RCPT/ARQ schemes are shown to outperform the other
two schemes in terms of both throughput and energy efficiency at the
cost of larger delay and complexity. In addition, maximum network
throughput is investigated for different ARQ schemes under energy
constraints
IEEE Journal on Selected Areas in Communications 09/2000; · 3.41 Impact Factor
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ABSTRACT: Modified ARQ protocols are known to improve the robustness and
throughput of wireless data networks. In this paper, a concatenated
Reed-Solomon (RS) punctured turbo coding ARQ scheme for DS/SSMA data
networks is presented. The system performance is evaluated for different
combinations of puncturing patterns and RS outer codes used over a
Rayleigh fading channel. The choice of the RS code rate and puncturing
pattern is shown to have a significant effect on the performance under
various channel conditions. The proposed system displays significant
throughput and delay performance improvement over the standard ARQ and
metric combining ARQ systems
Vehicular Technology Conference, 1999 IEEE 49th; 08/1999
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[show abstract]
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ABSTRACT: Modified ARQ (automatic-repeat-request) techniques based on turbo
coding are investigated for asynchronous DS-CDMA (direct-sequence
code-division multiple-access) data networks under shadowing and
frequency selective fading channel conditions. The throughput, delay,
and energy efficiency performance of standard ARQ, metric combining, and
RCPT (rate compatible punctured turbo) coded ARQ schemes are compared
via simulations. The RCPT/ARQ schemes are shown to outperform the other
two schemes in terms of both throughput and energy efficiency at the
cost of larger delay and complexity. Maximum network throughput is
investigated for different ARQ schemes under energy constraints
Military Communications Conference Proceedings, 1999. MILCOM 1999. IEEE; 02/1999
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ABSTRACT: The concept of a general nonlinear parity-check equation was first
proposed by Pietrobon et al. who used them to construct rotationally
invariant trellis codes for two dimensional signal sets. This paper
applies this technique to trellis-coded modulation (TCM) codes with
multidimensional MPSK and MQAM constellations to construct nonlinear
phase rotationally invariant multi-D codes. Based on this construction
technique, a series of the best fully phase rotationally invariant
multi-D trellis codes for a variety of signal constellations is obtained
through a systematic code search program. The code search results show
that most codes achieve the same asymptotic coding gain as the best
linear, but nonphase rotationally invariant codes found by Pietrobon et
al
IEEE Transactions on Communications 11/1997; · 1.68 Impact Factor
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Tingfang. Ji
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ABSTRACT: A network coexistence methodology is investigated for robust coexistence of an arbitrary set of non-collaborative networks. It is shown that maximizing the energy efficiency of each node is the key to the capacity maximization for the coexisting networks. Unlike existing pairwise coexisting schemes, a two level distributed algorithm is proposed without resorting to any knowledge of the physical layer and MAC layer protocols of interfering networks. The coexistence scheme is formulated as an N-person noncooperative power-controlled coexistence game (NPCG) whose convergence and optimality properties are discussed from a game theory view point. One interesting property of the game is that the Nash equilibrium of the game is on the Pareto frontier, i.e., a social optimal of the distributed networks.
Global Telecommunications Conference, 2004. GLOBECOM '04. IEEE;
