In a wireless communication technique well-known in the art, an uplink (referred to as an up or uplink) generally means a line through which data are transmitted from a mobile station apparatus to a base station apparatus when the base station apparatus and the mobile station apparatus communicate with each other in a cellular communication or the like. In this uplink, the base station apparatus receives signals from various mobile station apparatuses simultaneously. Therefore, if the reception powers are equal, the reception process becomes easy and reception characteristics become also excellent. In order to realize this, a system which controls a transmission power of a signal which a mobile station apparatus transmits has been introduced, which is referred to as transmission power control (TPC: Transmit Power Control).
A communication system currently used in a mobile phone of 3G (third generation) is CDMA (Code Division Multiple Access), and a plurality of mobile station apparatuses uses different codes, and accesses a base station apparatus simultaneously using the same frequency, and consequently, the TPC which is highly accurate and high-speed is generally needed. On the other hand, in the specification of a next-generation (3.9G) mobile phone, DFT-S-OFDMA (Discrete Fourier Transform-Spread-Orthogonal Frequency Division Multiple Access) is scheduled to be used as a communication system of an uplink, and the highly precise and high-speed TPC like the TPC used in the CDMA is not considered to be necessary. However, for the purpose of controlling appropriately an interference amount to an adjacent base station apparatus, the TPC has been standardized (Non-patent Document 1).
The TPC method is classified broadly into two types, and one is referred to as an open loop and the other, a closed loop. Performing description briefly assuming that the TPC is used in an uplink, the open loop TPC is one in which a mobile station apparatus controls a transmission power at it's own decision, and the closed loop is one in which a mobile station apparatus controls a transmission power at the direction of a base station apparatus.
As for the open loop, there is a method which estimates a signal attenuation quantity from the transmission power which a base station apparatus transmits and the reception power which the mobile station apparatus actually receives, and determines the transmission power of the mobile station apparatus from the estimated attenuation quantity and the reception power which is needed at the base station apparatus. On the other hand, as for the closed loop, there is a method which measures a reception power at the base station apparatus and notifies the mobile station apparatus of a shortage/overage, or a method that notifies the mobile station apparatus of an increase/decrease of the transmission power thereof from an error rate of the transmitted signal or the like.
In addition, as for a next “next generation” (4G), a technique of Carrier Aggregation which uses the systems standardized in the 3.9G in parallel in a plurality of different bands to make them as one system is investigated. There is a merit that a throughput can be simply improved by this technique.
USPTO Backgrounds
USPTO Backgrounds