Wireless Communications

A cellular base station serves a multiplicity of single-antenna terminals over the same time-frequency interval. Time-division duplex operation combined with reverse-link pilots enables the base station to estimate the reciprocal forward- and reverse-link channels. The conjugate-transpose of the channel estimates are used as a linear precoder and combiner respectively on the forward and reverse links. Propagation, unknown to both terminals and base station, comprises fast fading, log-normal shadow fading, and geometric attenuation. In the limit of an infinite number of antennas a complete multi-cellular analysis, which accounts for inter-cellular interference and the overhead and errors associated with channel-state information, yields a number of mathematically exact conclusions and points to a desirable direction towards which cellular wireless could evolve. In particular the effects of uncorrelated noise and fast fading vanish, throughput and the number of terminals are independent of the size of the cells, spectral efficiency is independent of bandwidth, and the required transmitted energy per bit vanishes. The only remaining impairment is inter-cellular interference caused by re-use of the pilot sequences in other cells (pilot contamination) which does not vanish with unlimited number of antennas.

Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas

Multiple-input multiple-output (MIMO) technology is maturing and is being incorporated into emerging wireless broadband standards like long-term evolution (LTE) [1]. For example, the LTE standard allows for up to eight antenna ports at the base station. Basically, the more antennas the transmitter/receiver is equipped with, and the more degrees of freedom that the propagation channel can provide, the better the performance in terms of data rate or link reliability. More precisely, on a quasi static channel where a code word spans across only one time and frequency coherence interval, the reliability of a point-to-point MIMO link scales according to Prob(link outage) ` SNR-ntnr where nt and nr are the numbers of transmit and receive antennas, respectively, and signal-to-noise ratio is denoted by SNR. On a channel that varies rapidly as a function of time and frequency, and where circumstances permit coding across many channel coherence intervals, the achievable rate scales as min(nt, nr) log(1 + SNR). The gains in multiuser systems are even more impressive, because such systems offer the possibility to transmit simultaneously to several users and the flexibility to select what users to schedule for reception at any given point in time [2].

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Scaling Up MIMO: Opportunities and Challenges with Very Large Arrays

The quintessential goal of sensor array signal processing is the estimation of parameters by fusing temporal and spatial information, captured via sampling a wavefield with a set of judiciously placed antenna sensors. The wavefield is assumed to be generated by a finite number of emitters, and contains information about signal parameters characterizing the emitters. A review of the area of array processing is given. The focus is on parameter estimation methods, and many relevant problems are only briefly mentioned. We emphasize the relatively more recent subspace-based methods in relation to beamforming. The article consists of background material and of the basic problem formulation. Then we introduce spectral-based algorithmic solutions to the signal parameter estimation problem. We contrast these suboptimal solutions to parametric methods. Techniques derived from maximum likelihood principles as well as geometric arguments are covered. Later, a number of more specialized research topics are briefly reviewed. Then, we look at a number of real-world problems for which sensor array processing methods have been applied. We also include an example with real experimental data involving closely spaced emitters and highly correlated signals, as well as a manufacturing application example.

Two decades of array signal processing research: the parametric approach

It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

The present disclosure relates to a technique for transmitting modulation symbols on multiple frequency resources. A method aspect of this technique includes applying a Discrete Fourier Transform (DFT) coding per set of modulation symbols of two or more sets of modulation symbols, wherein a first set of modulation symbols from the two or more sets of modulation symbols is transmitted on a set of frequency resources handled by the same power amplifier. Then, Orthogonal Frequency Division Multiplexing (OFDM) modulation is applied to the sets of DFT coded modulation symbols to output a first set of OFDM symbols for transmission on the set of frequency resources, and output another set of OFDM symbols for transmission on at least one additional frequency resource distinct from the set of frequency resources. Power amplification is then applied per set of frequency resources at the power amplifier.

A transmitter stage and a corresponding method for signal transmission on mutiple compenent carriers in a telecommunication system

Methods and apparatus for signaling scheduling information in a spatial multiplexing wireless communications system (700), as well as corresponding methods and apparatus for processing such signaling information, are disclosed. An exemplary method for signaling scheduling information comprises scheduling (310, 420) first and second transport blocks (110) for simultaneous transmission during a first transmission interval on first and second data substreams, respectively, and further comprises assigning (320, 430) a single re-transmission process identifier for the first transmission interval and transmitting(330, 440) first scheduling information for the first transmission interval. The first scheduling information comprises the re-transmission process identifier and first disambiguation data. The method further comprises scheduling (360, 470) at least one of the first and second transport blocks (110) for re-transmission during a second transmission interval and transmitting (370, 495) second scheduling information for the second transmission interval, the second scheduling information comprising the re-transmission process identifier and second disambiguation data. The first and second disambiguation data indicate whether the re-transmission of the retransmitted transport block (110) is scheduled for the first or second data substream and may be used by a receiver to determine the same.

Telecommunication system and error control in such system

상이한 라디오 액세스 기술들에 기초하여 동작하는 네트워크 유닛(20, 30) 및 하나 이상의 연관된 무선 통신 디바이스(10-1, 0-2)가 제공된다 다운링크(DL)에서, 제1 RAT의 네트워크 유닛(20)은 제2 RAT의 주파수 채널보다 높은 제1 RAT의 주파수 채널에서 5 DL 캐리어를 송신하도록 구성된다 따라서, 무선 통신 디바이스(10-)는, 제2 RAT의 주파수 채널보다 높은 제1 RAT의 주파수 채널에서 제1 RAT의 DL 캐리어를 수신 및 복조 및/또는 디코딩하도록 구성된다 업링크(UL)에서, 무선 통신 디바이스(10-1)는, 제2 RAT의 업링크 주파수 채널과 중첩하는 업링크 주파수 채널에서 제1 RAT의 UL 캐리어를 송신하도록 구성된다 따라서, 네트워크 유닛(20)은, 제2 RAT의 업링크 주파수 채널과 중첩하는 업링크 주파수 채널에서 제1 RAT의 업링크(UL) 캐리어를 수신 및 복조 및/또는 디코딩하도록 구성된다

Stefan Parkvall

Papers

A transmitter stage and a corresponding method for signal transmission on mutiple compenent carriers in a telecommunication system

Telecommunication system and error control in such system

상이한 라디오 액세스 기술들과 관련된 업링크 및/또는 다운링크 시그널링