1. Field of the Invention
The invention relates to a transmission method and a base transceiver station in a cellular telecommunication system.
2. Description of the Related Art
Transmit diversity, especially transmit antenna diversity, is an attractive means of obtaining diversity gain against fading mechanisms, such as Rayleigh fading, of a radio channel in telecommunications systems. An approach for providing diversity gain by way of antenna diversity is an antenna hopping method, which consists of transmitting consecutive information bursts from a base transceiver station by using different antennas. An antenna transmitting the information burst may be selected based on a periodical or pseudorandom antenna hopping sequence, for example. The gain in transmission is achieved provided that the radio channels transmitted from each antenna are exposed to different multi-path fading.
A characteristic of the antenna hopping method arises from discontinuity in the base transceiver station transmission when the transmitting antenna is changed from one to another. The discontinuity poses difficulties when a carrier subjected to the antenna hopping is required to provide correlated time slots, for example, for channel characterization purposes. The problem of discontinuity occurring in such carriers may be solved by leaving out such carriers from the antenna hopping, and by confining the antenna hopping to carriers in which the problem of discontinuity is small compared to the gain obtained with the antenna hopping.
A portion of time slots transferred by a carrier left out from the antenna hopping, however, may be used in information payload transmission, and leaving carriers out from the antenna hopping results in latent radio resources. Therefore, it would be a great benefit to be able to increase the number of carriers to which the antenna hopping may be applied.