In existing wireless technologies, signal repeating devices, or “repeaters” are used to extend the coverage of the overall wireless system. For example, often such wireless or cellular systems consist of a plurality of base stations that communicate with each other in an overlapping fashion, and operate to provide a defined signal coverage area for user equipment (“UE”), such as a cell phone or other wireless device. In such coverage areas, there are often smaller, more remote areas that have very low signal reception, such as areas within buildings or areas that are otherwise obstructed. Rather than implementing another costly and large base station to provide coverage to such low signal areas, signal repeating devices or repeaters are utilized.
A repeater essentially has a donor antenna that is in communication with one or more base stations. The repeater receives downlink signals from the base station, processes and amplifies those signals, and then transmits those signals through a coverage antenna into the remote area that otherwise has low signal reception or low signal power. For example, referring to FIG. 1, a portion of a wireless communications system 10 might include a base station 12 that communicates with a repeater 14 having a donor antenna 16, a coverage antenna 18, and processing electronics 20 that are configured to process and amplify the repeated signal. Accordingly, downlink wireless signals 22 from the base station 12 are received by the donor antenna 16 of the repeater 14. The signals are then amplified and repeated to be transmitted through the coverage antenna 18 as downlink signals 22a. The repeated downlink signals 22a are transmitted into the remote area and are received by the UE that may include one or more wireless communication devices, such as cell phones 24, as show in FIG. 1. Similarly, in an uplink direction, as indicated by reference numerals 26 and 26a, the UE devices 24 communicate signals back to the coverage antenna 18, and the repeated signal 26 is then transmitted as an uplink signal back to the base station 12. As would be readily understood by a person of ordinary skill in the art, such repeater devices 14 can take many different forms.
One particular performance characteristic of a repeater is the gain of the repeater, or the amount of amplification that the repeater provides in the repeated signal. In many applications for a repeater within a wireless system, it is desirable to vary the gain of the repeater based upon certain signal transmission parameters. For example, in a spread spectrum system, such as a CDMA system that utilizes spread spectrum signal traffic, it may be desirable to lower the gain of the repeater based upon the absence of any spread spectrum signal traffic through the repeater. Otherwise, a repeater that continuously operates at a high gain may very likely increase the interference level within the wireless coverage area. Spread spectrum signals appear generally noise-like in structure, and are thus, susceptible to the overall noise figure within the wireless system. The overall network capacity within a spread spectrum communication network is a function of the interference or noise level within that network. As such, it is desirable to automatically adjust the gain, and specifically lower the gain when there is no signal traffic through the repeater. Conversely, when signal traffic is present, it would be desirable to increase the repeater gain.
There is an inherently difficult problem in automatically controlling the gain of a repeater within a spread spectrum system based upon the existence or absence of the spread spectrum signal. In spread spectrum technology, the signals are subject to spreading codes, which are often called “Pseudo Noise” (“PN”) codes. Because of the noise-like structure of the signals, they are difficult to detect at a repeater when the spreading codes are not known. As such, it becomes difficult to automatically adjust the gain of a repeater based upon such signal detection.
Accordingly, there exists a need in the art to provide gain control within a repeater, and particularly to provide gain control in a network utilizing spread spectrum signals.