Radio communications device with adaptive combination

Abstract

To reduce costs in multiple-input multiple-output (MIMO) and other wireless communication systems an arrangement is described whereby adaptive combination is used at user equipment in order to produce two or more directional antenna beams. Improvements in carrier to interference levels result.

Description

[0001] The present invention relates to radio communications devices with adaptive combination.BACKGROUND TO THE INVENTION[0002] The demand for wireless communication systems has grown steadily over recent decades, and has included several technological jumps over this time, particularly in the area of cellular and wireless local area network (WLAN) communication systems. Analogue cellular phones have been replaced with digital handsets using for example GSM and CDMA technologies, and so called third generation systems such as UMTS are now being introduced. Similarly WLAN technologies such as HyperLan and IEEE 802.11b are also being introduced. The number of users continues to increase and data traffic is now becoming an important part of the wireless network. Both of these factors mean that it is important for operators to look for methods of increasing the capacity of their networks to meet future demands.[0003] As well as the need to increase capacity there is a general requireme...

AI Technical Summary

Benefits of technology

[0015] This provides the advantage that directional antenna beams are used in a communications system which, for a plurality of such devices in a network, reduces overall carrier to interference levels and hence increases capacity. The device may be either a basestation or a user terminal. For example, the user terminal can be a mobile telephone, a personal digital assistant, a personal computer, a subscriber premises installation or any other suitable type of terminal. Also, the combiner preferably comprises at least one beamformer or the antenna elements are provided as a phased array. Preferably, the communications system is a multiple-input multiple-output communications system. In this case the advantages of increased data rates are achieved in addition to improvements in carrier to interference levels.

[0018] The combiner is preferably arranged to electronically steer the directional antenna beams. This provides the advantage that problems associated with spatial fading are addressed by steering the beam. Also, because the direction of the antenna beams can be adjusted, pointing losses are reduced as compared with systems that use fixed directional beams.

Problems solved by technology

One performance related problem relates to multipath fading.

Incoming scattered signals can add constructively or destructively depending on the relative amplitude and phase of the different components.

When one of those signals is in a fade the other is typically unfaded.

However, one problem with known MIMO arrangements is that they are relatively expensive in the respect that multiple antennas are required together with multiple transmit and receive chains.

Receive chains are relatively expensive, bulky and power must be provided to each of those receive chains.

This is particularly disadvantageous for user terminals that are required to be compact and also for basestations which need to be unobtrusive.

Similar problems occur for transmit chains.

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