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

5G is the next step in the evolution of mobile communication and a key component of the future networked society. With capabilities such as massive system capacity, higher data rates, very low latency and ultra-high reliability, 5G will provide significantly enhanced mobile-broadband experience but also support a wide range of new wireless applications and use cases. In this paper, a trial system for 5G mobile broadband operating at 15 GHz is outlined, together with initial experimental results showing that multi-Gbps data rates are possible.

A Trial System for 5G Wireless Access

In MU-MIMO scenarios, a target terminal (220) can be exposed to data streams intended for other terminals (222). If the target terminal (220) is capable of interference cancellation, then a network node (300), such as a base station (210) or RNC (205), can provide the target terminal (220) with interference information so that the target terminal (220) can efficiently cancel interferences due to these interfering data streams. The interference information may include one or more interfering configuration, each of which characterizes a related interfering data stream. The interference information can also include the identity of the other terminal (222) that is the intended recipient of the interfering stream. The network node (300) may determine whether the target terminal (220) can benefit from the interference information. If so, the network node (300) can provide the interference information to the target terminal (220).

Signaling data channel's configuration information to facilitate interference cancellation

Systems and methods are disclosed for using multiple configuration groups having corresponding configuration identity (CID) parameters to configure a transmission channel and a reception channel for a user equipment device in a cellular communication network. In one embodiment, a user equipment device in a cellular communication network obtains CID values for CID parameters for a number of configuration groups. Each of the configuration groups includes one or more transmission channel or reception channel parameters. For each of the configuration groups, the user equipment device configures the parameters in the configuration group based on the CID value obtained for the CID parameter for the configuration group. In this manner, the transmission channel and the reception channel for the user equipment device are configured based on multiple CID values rather than a single physical layer cell identifier for a cell in which the user equipment device is located.

Independent configuration identities in a heterogeneous cellular communication network

Methods may be provided to operate a network node of a radio access network. Such methods may include transmitting first control information to a wireless terminal, and the first control information may define a frequency resource available for data communication with the wireless terminal over a subframe. After transmitting the first control information, second control information may be transmitted to the wireless terminal. The second control information may define a time resource for a sub-subframe of the subframe. Communication of data may be provided between the network node and the wireless terminal during the sub-subframe of the subframe defined by the frequency resource of the first control information and the time resource of the second control information. Related network nodes and wireless terminals are also discussed.

Defining sub-subchannels for data communication using separately provided frequency and time resources and related wireless terminals and network nodes

Method and apparatus in a communication unit (400) employing a wireless TDD or half duplex FDD transmission arrangement when communicating with a data sending party, for scheduling feedback reports for data blocks in received RX sub-frames, in TX sub-frames available for transmission. An obtaining unit (402) in the communication unit receives allocation parameters (P) for the connection where the number of required feedback reports is greater than the number of allowed feedback reports. A scheduling unit (404) in the communication unit then schedules feedback reports (FR) in available TX sub-frames according to a predetermined spreading rule also known by the data sending party, dictating that the feedback reports are spread out or distributed evenly over the available TX sub-frames. In this way, the number of feedback reports in a TX sub-frame can be reduced.

Stefan Parkvall

Papers

A Trial System for 5G Wireless Access

Signaling data channel's configuration information to facilitate interference cancellation

Independent configuration identities in a heterogeneous cellular communication network

Defining sub-subchannels for data communication using separately provided frequency and time resources and related wireless terminals and network nodes

Method and apparatus in a telecommunication system