Orthogonal Frequency Division Multiple Access (OFDMA) communication systems have been proposed for use in Long Term Evolution (LTE) and WiMAX communication systems for transmission of data over an air interface. In OFDMA communication systems, a frequency bandwidth is split into multiple contiguous frequency sub-bands, or sub-carriers, that are transmitted simultaneously. A user may then be assigned one or more of the frequency sub-bands for an exchange of user information, thereby permitting multiple users to transmit simultaneously on the different sub-carriers. These sub-carriers are orthogonal to each other, and thus intra-cell interference is reduced.
To maximize the spectral efficiency, a frequency reuse factor of one has been proposed for both a downlink and an uplink in OFDMA communication systems. With a frequency reuse factor of one, data and control channels in one sector or cell site will likely experience interference from the same resources being un use in other sectors or cell sites. This is especially true for user equipment (UEs) at the edge or boundary of a sector or cell site or at bad coverage locations. A user located close to the cell site but near a sector boundary will not only support a very high speed, high C/I rate into the desired sector, but will also generate a very high interference noise rise into those same resources on the adjacent sector potentially rendering those adjacent sector resources unusable. On the other hand, implementation of a traditional power control scheme, wherein each UE in a sector or cell site transmits at an uplink power that results in a same received power at an enhanced NodeB for each such UE, suffers from a low overall spectral efficiency due to a lack of UEs that can transmit at high data rates.
One solution to the problem has been to treat UEs that are close-in to the cell site differently than those that are located at the edge or boundary of a sector or cell site or at bad coverage locations. Current mechanisms such as in the LTE standard use a fractional power control “alpha” parameter to generically reduce available transmit power to all close-in users based on path loss. This reduces the problem, but does not eliminate the problem. In particular, this solution may not fix high interference into adjacent sectors, but just reduce the probability of interference. In addition, this solution reduces power (and throughput) even to users not causing interference with the end result being the UE is forced to use less power than actually required and thus experiences a reduced user data throughput
Therefore, a need exists for resource allocation scheme that does a better job of managing interference into adjacent sectors or cell sites than the current algorithms
Skilled artisans will appreciate that common but well-understood elements that are useful or necessary in a commercially feasible embodiment are typically not depicted or described in order to facilitate a less obstructed view of these various embodiments of the present invention.
USPTO Backgrounds
USPTO Backgrounds