This Small Business Innovation Research (SBIR) Phase II project targets significantly increased throughputs and distances for broadband access over the existing copper landline infrastructure at low cost. In particular, the technology being developed offers advantages in interference-dominated and in suburban/rural environments. In the USA alone there are many millions of households that are currently out-of-reach of broadband access, where there are typically multiple copper landlines available, and the global demand for such solution is significantly higher. For these underserved subscribers, this innovative extended-reach solution represents the only low-cost broadband access alternative to costly, inefficient satellite coverage. While existing Digital-Subscriber-Line (DSL) solutions are not specified to provide broadband access at very long distances, the company?s novel solution greatly increases the achievable distances and allows broadband rates (1Mbps) to be delivered at extended ranges, as demonstrated in Phase 1 of this project. The technology combines innovative signal-processing algorithms with novel digital implementation architectures to allow for high-performance reduced-complexity and low current-consumption implementations.
The broader impact and commercial potential of this project are in enabling affordable broadband service to the many households, which are currently out of the reach of broadband access, and in enhancing the performance of other copper-based applications. The technology will enable telco providers to better compete in areas where cable service exists, and can enhance existing solutions for copper-based backhaul, thereby helping service providers with the growing problem of backhaul bottlenecks associated with increased wireless traffic. The growing demand for solutions of this type has the potential to generate annual revenues on the order of $50M, representing a great business opportunity. Societal benefits include providing broadband service to previously-unreachable homes, thus allowing them to engage in remote education, e-commerce, and telecommuting, with all of the advantages that these entail. Ongoing collaborative research with local universities is serving to steer academic research in this field towards the actual needs and interests expressed by service providers, thus advancing the related fields in communication theory and circuitry design and involving students in this research.
Normal 0 false false false EN-US X-NONE BN-BD Xtendwave has developed a digital signal-processing technology to mitigate the throughput-limiting interference in 4G LTE networks and thereby maximize their capacity. LTE carriers reuse the limited available licensed spectrum in each cell and across the multiple tiers within a cell. This practice increases spectral efficiency while introducing throughput-limiting inter-cell and intra-cell interference, as shown in Figure 1. Intercell inference, which originates from an adjacent cell, can limit the reception primarily in the mobile devices that are placed close the cell boundary that is close to the interfering cell. Contrarily, intra-cell interference, resulting from the simultaneous use of the same time-frequency resources to serve multiple users within the same cell, can be as strong as the desired signal throughout the entire cell. State-of-the-art interference cancellation/co-ordination techniques can be classified into two main approaches: transmitter-based and receiver-based. Transmitter-based approaches implement inter-cell interference coordination, which applies certain restrictions to the transmit power and time-frequency resource allocation in a cell to improve cell-edge performance in neighboring cells. However, these techniques require extensive information exchange between neighboring cells and feedback from users, which increases signaling overhead and latency. In addition, these approaches cannot address intra-cell interference in multiple spatial layer transmission scenarios. Receiver-based approaches implement algorithms for interference cancellation rather than avoidance, allowing different co-scheduled users to use the same time/frequency resources, thereby resulting in more efficient use of network resources. The prohibitive implementation complexity of the joint maximum-likelihood (ML) approach makes it impractical for joint-ML based decoding to support the mandatory LTE constellations for multiple spatially-multiplexed transmission layers, as required by LTE-A. The industry standard minimum mean square error interference rejection combining (MMSE-IRC) detector only mitigates inter-cell interference. Its performance is significantly degraded in multi-layer transmission modes. Another known technique, based on beam-forming at the receiver, may be limited in its ability to combat intra- or inter-cell interference in many practical scenarios. The solution developed by Xtendwave (XWICTM) can simultaneously mitigate both inter- and intra-cell interference in an LTE receiver equipped with two or more receiver antennas. The efficient unified implementation of interference mitigation enables XWICTM to outperform alternative receiver-based solutions. In addition, the XWICTM technology is capable of mitigating interference in both LTE downlink data and control channels. The achievable data throughput in a device enhanced with the XWICTM module, as shown in Figure 2, is much higher than that of a device employing state-of-the-art MMSE-IRC (for single-layer transmission), particularly when the intra-cell interference is much stronger than the inter-cell interference. A XWICTM-based device offers up to double the throughput, as shown in Figure 3, that is achievable by an alternative MMSE-LE based solution (for dual-layer transmission). Compared to MMSE-IRC, the gate-count in a hardware based implementation for the XWICTM module is at most ~3× higher but a paltry 5% addition to the overall silicon footprint of the LTE baseband modem. The XWICTM module achieves virtually the same performance as the prohibitively-complex joint-ML approach, while offering considerably reduced implementation complexity and cost. The performance gains achieved through the use of the XWICTM technology benefit the entire LTE ecosystem, ranging from content providers to end users. For the content providers the capacity gains allow for high-quality multimedia, including streaming of high-definition (HD) video. Network providers can leverage the gains by increasing the capacity in congested networks and supporting more users. Manufacturers of mobile devices and of chips equipped with XWICTM will be able to offer product differentiation. Finally, the end users will experience enhanced quality of service and overall experience.
