Inter-cell interference (ICI) management is necessary to obtain maximum performance from a wireless communications system. One area of increased focus in recent years is the development of techniques that employ multi-cell coordination to reduce ICI. In most cases, it is highly desirable to keep coordination signaling between cells to a minimum for reasons of cost, complexity, and latency. For VoIP applications, it is also important to manage the uplink feedback due to the large number of connections that must be simultaneously supported.
Over the years, a variety of methods have been developed for reducing ICI or mitigating the impact of ICI. Some of the earliest techniques were designed for implementation primarily at the interference-producing cell in order to control the level of interference that was transmitted out of a cell. Probably the best-known example of this class of techniques is simple transmit power control (TPC) which attempted to reduce the level of interference reaching the co-channel cell by minimizing the transmit power within the serving cell to the minimum level required for acceptable performance. Another method that can arguably be placed in this category is fractional frequency reuse (FFR), where each frequency was only reused in non-adjacent cells in order to provide isolation between the co-channel cells and allow a transmitted signal to attenuate sufficiently before reaching its co-channel cell. Later, a group of methods were designed for implementation at the receiving cells in order to mitigate or cope with the interference that did arrive from out of a cell. Techniques falling into this category include interference averaging through the use of different subcarrier permutations or hopping patterns, successive interference cancellation (SIC), and certain MIMO techniques such as interference nulling.
USPTO Backgrounds
USPTO Backgrounds