Abstract
Coordinated multipoint (CoMP) from long term evolution (LTE)-advanced is a promising technique to enhance the system spectral efficiency. Among the CoMP techniques, joint transmission has high communication requirements, because of the data sharing phase through the backhaul network, and coordinated scheduling and beamforming reduces the backhaul requirements, since no data sharing is necessary. Most of the available CoMP techniques consider perfect channel knowledge at the transmitters. Nevertheless for practical systems this is unrealistic. Therefore in this study the authors address this limitation by proposing a robust precoder for a multicell-based systems, where each base station (BS) has only access to an imperfect local channel estimate. They consider both the case with and without data sharing. The proposed precoder is designed in a distributed manner at each BS by maximising the signal-to-leakage-and-noise ratio of all jointly processed users. By considering the channel estimation error in the design of the precoder, they are able to reduce considerably the impact of these errors in the system's performance. The results show that the proposed scheme has improved performance especially for the high signal-to-noise ratio regime, where the impact of the channel estimation error may be more pronounced.
Highlights
Multicell cooperation is a promising solution for cellular wireless systems to mitigate intercell interference, improving system fairness and increasing capacity in the years to come [1,2,3], and is 30 already under study in LTE-advanced under the coordinated multipoint concept [4]
There are several cooperative multicell approaches depending on the amount of information shared by the transmitters through the backhaul network and where the processing takes place, that is, centralised if the processing takes place at the central unit (CU) [5] or distributed [2, 6] if it takes 35 place at different transmitters
In [10], a clustered base stations (BSs) coordination is enabled through a multicell block diagonalisation (BD) strategy to mitigate the effects of interference in multicell multiple-input– multiple-output (MIMO) systems
Summary
Multicell cooperation is a promising solution for cellular wireless systems to mitigate intercell interference, improving system fairness and increasing capacity in the years to come [1,2,3], and is 30 already under study in LTE-advanced under the coordinated multipoint concept [4]. Two centralised multicell precoding schemes based on the waterfilling technique have been proposed in [8]. A BD cooperative multicell scheme was proposed in [11] where the weighted UTs sum-rate 55 achievable is maximised. Distributed precoding schemes based on zero-forcing (ZF) criterion with several centralised power allocation approaches, which minimise the average bit error-ratio (BER) and sum of inverse of signal-to-noise ratio was proposed in [15]. One of the considered criteria to design the precoders was the signal-to-leakage-and-noise (SLNR) ratio maximisation, introduced 95 first in the context of multiuser MIMO [17] This technique balances the received signal power of the target user against the interference power imposed on the remaining users.
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