Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
2000-05-05
2001-10-23
Chang, Vivian (Department: 2682)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S067150, C455S517000, C370S528000
Reexamination Certificate
active
06308081
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a transmission method used during DTX in a radio system comprising a base transceiver station acting as a transceiver and subscriber terminals acting as transceivers which establish a connection with each other with a signal transmitted through the base transceiver station, for which connection a radio channel is formed, in which a signal coded by the transceiver is transmitted.
BACKGROUND OF THE INVENTION
In a cellular radio system, discontinuous transmission, or DTX, is used to reduce interference and the power consumption of a subscriber terminal. The above-mentioned cellular radio system can be a GSM system, for instance. DTX is used during breaks in speech. During DTX, the subscriber terminal usually only transmits a silence descriptor frame, i.e. SID frame. A SID frame is normally transmitted once every 480 ms.
A SID frame is typically used to generate noise in a subscriber terminal in DTX mode. If a noise of suitable magnitude was not generated, the receiver would find the silence caused by breaks uncomfortable. In the worst case, the receiver would think that the connection has been broken. During breaks in speech, the coder enters DTX mode during which SID frames are transmitted. The SID frames transmitted during breaks in speech comprise various update data. The receiver uses the update data when generating noise, for instance. The SID frames are also used to measure the quality of the radio channel. If SID frames are used in a GSM system, for instance, the measurement period is 480 ms.
A transceiver of a radio system can in some cases very quickly need information on the changes taking place in the radio channel. This means that apparatuses in radio systems must receive updated information on the status of the data and radio channel at a fast pace. An apparatus of the kind mentioned above is for instance an AMR transceiver (AMR=Adaptive Multirate) which requires a fast adaptation rate. In addition, radio systems need to transmit data concerning the channel mode of a speech codec, for instance.
In current radio systems, a transmitter can transmit the above-mentioned data during DTX only in predefined TDMA frame locations. TDMA frame locations are the same frame locations in which information on the background noise during breaks in speech is also transmitted. Prior art systems are relatively inflexible, because they use fixed transmission periods for transmitting the above information.
Radio systems thus need to transmit control commands as often as possible to a coder and decoder concerning the AMR mode, for instance. The problem with prior art radio systems is the slow rate of adaptation. Adaptation could be accelerated by blocking DTX in both transmission and reception directions, for instance. This way, control information could be transmitted in each frame. The above-mentioned method would, however, lead to loosing at least a part of the benefit derived from DTX. In practice, loosing benefit means that the battery operation time would not be extended. The amount of interference would also probably increase.
Another problem is the slow transmission rate of the control data required by the AMR codec. As mentioned earlier, for optimum operation, the AMR codec requires information on the status of the channel and the codec mode, for instance. However, the transmission of the above-mentioned data takes relatively long in prior art systems. The slowness of the transmission has resulted in not getting the best possible benefit out of the AMR in DTX mode.
BRIEF DESCRIPTION OF THE INVENTION
It is thus an object of the invention to implement a transmission method and a radio system so as to solve the above-mentioned problems. This is achieved by the type of transmission method disclosed in the preamble, characterized by measuring a signal received from a radio channel, transmitting during DTX frames placed in a frame structure to the radio channel on the basis of the received measurement result, freely placing at least some of the frames anywhere in the frame structure to be transmitted, transmitting information in the frames to a transceiver which communicates with a transceiver in DTX mode, and altering the operation of the transceiver, which receives the above-mentioned frames, on the basis of the information in the frames.
A further object of the invention is a radio system comprising a base transceiver station acting as a transceiver and subscriber terminals acting as transceivers which establish a connection with each other with a signal transmitted through the base transceiver station, for which connection a radio channel is formed, in which a signal coded by the transceiver is transmitted, and in which radio system the transceiver comprises transmission means which transmit frames when the transceiver is in DTX mode.
The radio system of the invention is characterized in that it comprises measuring means which measure the signal received by the transceiver from the radio channel, and transmission means which during DTX transmit information on frames to the radio channel on the basis of the measurement results received from the measuring means, of which frames at least some are freely placed by the transmission means in the frame structure to be transmitted, after which the transmission means transmit the frames to the transceiver which is connected to a transceiver in DTX mode, and the transceiver receiving the frames alters its operation on the basis of the information in the frames.
The preferred embodiments of the invention are set forth in the dependent claims.
The invention is based on the idea that a transceiver in DTX mode uses an optimum quantity of fixed frames per measurement period in measuring a radio channel. If the fixed frames are SID frames, for instance, the unused SID frames can be transmitted when necessary. The transmission of SID frames is thus not in any way bound to the frame structure used.
The transmission method and radio system of the invention provide several advantages. A transceiver in DTX mode receives during a measurement period preferably only one fixed SID frame which is used for measuring the quality of the radio channel. In the method, preferably a maximum of one fixed SID frame is used in an SACCH multiframe. Other SID frames can be transmitted when necessary. This way, the method becomes more flexible. The above-mentioned frame does not, however, necessarily have to be a SID frame, but it can be any other frame containing control and measurement data.
Since SID frames can also be transmitted when necessary, control data can be quickly transmitted to for instance an AMR codec, which makes it possible for the codec to quickly adapt to the signal. Extra SID update frames are only transmitted when the changes in the radio channel are extensive enough. Thus, the average benefit derived from DTX remains good all the time. The method enables transmitting SID frames, channel control data and measurement data at a very fast pace.
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Copy of International Search Report for PCT/FI99/00721.
Altera Law Group, LL
Appiah Charles N.
Chang Vivian
Nokia Networks Oy
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