Mitigating interference to maximize spectral efficiency in 3G/4G networks
With the advent of data applications, interference is a challenge for wireless carriers. Consequently, mitigating interference to maximize spectral efficiency and improve network throughput is on the minds of operators and handset makers. This article describes an interference cancellation technology comprising an ASIC/core hardware and DSP-based software, which cancels interference from all traffic channels, and from all interfering sources for 2.5G, 3G and 4G networks.
Canceling intracell interference induced by channel effects and intercell interference introduced by channel effects, as well as serving and non-serving base stations is a technological challenge. And, it is particularly difficult when the code space is heavily loaded, as in dense voice networks such as fully loaded CDMA2000 1xEV-DO data networks or mixed-voice and HSDPA networks.
While there may be several receiver architectures in the market to address the interference challenge, in reality there are four general classes of baseband receivers. And, in terms of increasing complexity, these include RAKEs, equalizers, linear minimum mean square error (MMSE) receivers, and multi-user detectors (MUDs). Each of these receivers is an optimum solution for a different combination of communication protocol, channel condition, and code-space loading. Consequently, when a RAKE is optimum, there is no performance gap to be filled by a more advanced receiver. However, when an equalizer is optimum, the only performance gap to be filled is between a RAKE and an equalizer. Likewise, when a linear MMSE receiver is optimum, there are performance gaps to be filled between a RAKE, an equalizer, and a linear MMSE receiver.
Thus, to fill available performance gaps between a RAKE, an equalizer, a linear MMSE receiver, at low complexity, TensorComm has developed a novel interference cancellation technology (ICT), comprising an ASIC/core hardware and DSP-based software, that cancels interference from all traffic channels, and from all interfering sources for 2.5G, 3G and 4G networks. A protean signal-processing operator, ICT exploits all time-varying source characteristics that code-space profiles and channel conditions leave open for exploitation, in a hardware-efficient architecture.
Interference sets the limit on performance in code-based systems.By canceling unwanted interference, ICT reduces power requirements and increases spectrum efficiency so that cells can maintain size and network capacity. The technology requires no modification to existing or evolving air interface standards. Because it is a receive-only technology, it requires no base station modification to effectively reduce interference on the forward link. It also can be integrated into CDMA and WCDMA chipsets today. The same technology may be applied to the reverse link and integrated into base stations. The important effect is to maintain cell size at high traffic density and to reduce the frequency of dropped calls in hand-off.
Besides canceling intersymbol and interchannel interference from pilot, paging, synchronization, traffic and high-rate data channels, ICT is specifically designed to cancel direct and multipath interference from adjacent base station sectors and interference from multipath within the serving sector. Also, this technology is complementary to, and can co-exist with, other technologies, such as transmit/receive diversity technologies, to re-capture power and/or spectral efficiency. Additionally, it is independent of carrier frequency bands, and will apply at 450 MHz, 800 MHz, 1900 MHz and elsewhere.
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© 2013 Penton Media Inc.
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