WO1999004586A1 - Radio transmission method and cordless phone mainly intended for dect standards - Google Patents

Abstract

The present invention relates to a radio transmission method between a transmitter apparatus and a receiver apparatus, wherein said method uses a service channel (area B) for transmitting voice signals and/or data signals as well as a signalling channel (area A) comprising an error correction symbol for transmitting signalling data. When a signalling pause is detected, the transmitter apparatus sends an identification signal for the signalling pauses (P) to the receiver apparatus through the signalling channel. The signals received during the reception of the identification signal for the signalling pauses at the service channel (area B) are not used by the receiver apparatus. Since the signalling channel includes an error correction, no signal can be reliably transmitted during the signalling pause at the receiver apparatus, thus avoiding the transmission errors that may occur upon transmission in the service channel during the signalling pause or subsequent to the actuation of a mute key.

Description

description

Radio transmission method and cordless telephone, especially for the DECT standard

The invention relates to a method for radio transmission between a transmitting device and a receiving device and a cordless telephone, in particular according to the DECT standard.

Digital cordless phones based on the DECT (Digital Enhanced Cordless Telephone) standard are becoming increasingly popular. The technical specification is described, for example, in David, Benter "Digitale Mobilfunkksyteme", Stuttgart, 1996, chapter 8.1. The air interface defined by DECT is based on a combination of FDMA (Freguency Division Multiple Access) and TDMA (Time Division Multiple Access). The available frequency spectrum from 1880 MHz to 1900 MHz is divided into ten carriers, each with a channel spacing of 1728 kHz. As shown in the attached FIG. 1, each carrier is divided into 24 time slots, which form a frame with a total length of 10 ms. The first twelve channels are reserved for the downlink from the handset to the base station and the following twelve time slots for the uplinks between base station and handset. A duplex connection is formed by a pair of time slots, for example time slot 11 and time slot 23. The uplink and downlink are then separated from each other by a duplex spacing of 5 ms.

Figure 2 shows, starting from the publication Components 31 (1993), Issue 6, pages 215 to 218; S. Althammer, D. Bruckmann: "Highly optimized ICs for DECT cordless phones" the basic circuit structure of the base station BS and the mobile part MT of a cordless phone system. The base station BS and the mobile part MT then have a radio part FKT with one for transmitting and receiving radio signals associated antenna ANT, a signal processing device SVE and a central controller ZST, which are connected to each other in the manner shown. The radio part FKT essentially contains the known devices such as transmitter SE, receiver EM and synthesizer SYN. Among other things, a coding

/ CODEC decoder included. The central control ZST has a microprocessor μP for the base station BS as well as for the mobile part MT with an OSI / ISO

Layer model [cf. (1): Unterrichtsblätter - Deutsche Telekom, Jg. 48, 2/1995, pages 102 to 111; (2): ETSI publication ETS 300175-1 ... 9, October 1992] built PGM program module, a signal control part SST and a digital signal processor DSP, which are interconnected in the manner shown. Of the layers defined in the layer model, only the first four layers that are essential for the base station BS and the mobile part MT are shown. The signal control part SST is designed in the base station BS as a time switch controller TSC and in the mobile part MT as a burst mode controller BMC. The essential difference between the two signal control parts TSC, BMC is that the base station-specific signal control part TSC takes on additional switching functions (switch functions) compared to the object part-specific signal control part BMC.

The principle of operation of the circuit units listed above is described, for example, in the publication Components 31 (1993), No. 6, pages 215 to 218.

Taking into account that, as mentioned, ten carrier frequencies are available, the total capacity is a total of 120 duplex channels. A DECT cordless system then automatically selects the channel with the best connection quality. In the lower part, FIG. 1 shows schematically the composition of a single time slot with a total of 416.6 μs duration, corresponding to 480 bits. First of all, a 60-bit protective band is present in order to enable the safe separation of adjacent time slots. Of the remaining 420 bits, 32 bits are used for synchronization (S field) and 4 bits for parity control (X field). A signaling channel (A field) accounts for 64 bits, of which 16 bits are an error code, for example Cyclic Redundancy Check (CRC). The remaining 48 bits are available for signaling, for example information for establishing a connection, exchange of identifiers, forwarding to another network cell (handover). The signaling rate of a duplex channel is therefore 64 bits / 10 ms = 6.4 kilobits / s. The data transmitted in the signaling channel are protected from transmission errors by the error correction bits. The 320 bits of the user channel (B field), however, are not specially protected against transmission errors. The transmission rate in a user channel is 32 kilobit / s.

DE-195 15 546 AI discloses a method and an arrangement for the wireless transmission of voice signals and of data signals over the same radio channel between a transmitting device and a receiving device. In the transmitting device, data signals are transmitted together with at least one control signal for identifying the pauses in speech via the same radio channel as the speech signals to the receiving device, in which the data signals are separated from the control signal and are output during the pauses in speech. In this way, when there are pauses in speech and speech signals are not sent, data signals can also be sent and received on the same radio channel. This leads to better utilization of the wireless radio transmission path with regard to information transmission in both transmission directions. From DE-42 36 088 AI a method for reducing disruptive effects of poor voice transmission quality in a telephone connection with a cordless telephone is known, in which the A field of a DECT burst is responsible for connection-accompanying information and in the case of telephone connections between a base station part and a handset of the cordless telephone set according to the DECT standard during the ADPCM transmission of speech due to bit errors, cracking and interference noises can be prevented by muting in the respective part of the cordless telephone set (muting of the speech signal).

If there are signal pauses in a DECT cordless telephone handset, for example due to a pause in the cordless telephone user's speech, either the ambient noise can be transmitted to the base station and then to the telephone partner in the B channel, or the terminal device transmits a silent signal when a signal pause is detected (courage signal, consisting of all ones) to the conversation partner. In the first case, the ambient noise can be perceived as being quite annoying, especially if the sensitivity of the microphone adapts to the detected signal level. If, in the second case, the mute signals are transmitted in the useful channel (B field), they are decoded on the receiving side like normal audio data and produce "silence" on the receiving loudspeaker when reception is error-free. However, if transmission errors occur with this mute signal, violent noise can occur instead.

The present invention is therefore based on the object of further developing a method for radio transmission between a transmitting device and a receiving device and a cordless telephone in such a way that the transmission quality is improved. In particular, the occurrence of interference signals or noise during a signal pause should be prevented. The invention proposes a method for radio transmission between a transmitter and a receiver, in which a signal pause identification signal is transmitted to the receiver when a signal pause is detected by the transmitter via the signaling channel (A field), whereupon the receiver during the reception of the Transmission pause identification signal, the signals received in the useful channel are not used, preferably not decoded and / or amplified. Since the signal pause identification signal is transmitted in the signaling channel (A field) protected against transmission errors, the occurrence of transmission errors during signal pauses can be significantly reduced.

The method according to the invention is particularly applicable to digital cordless telephones according to the DECT standard.

The invention also proposes a cordless telephone which has a device for detecting a signal pause and a device for transmitting a signal pause identification signal when a signal pause is detected.

The principle of operation of the method according to the invention is explained below by way of example with reference to the figures in which

FIG. 1 schematically shows an example of a time frame structure used in the method according to the invention;

Figure 2 is a block diagram of a known cordless telephone system according to the DECT standard.

Cordless phones are usually used in a combination of a base station and one or more mobile stations. The signals are forwarded by radio from the mobile station to the base station, which in turn is Fixed network is connected and transmits the signals to the interlocutor, who can use a landline phone, a cordless phone or a cell phone or the like. Time slots 0 to 11 are reserved for the transmission of signals from the base station to the handset, time slots 12 to 23 are reserved for the transmission of signals from the mobile device to the base station (uplink). , Be formed as shown base station and handset can, as i ^"FIG. 2, the central control unit ZST of Mo bilteils MT but additionally includes means that a signal pause, ie, a speech pause of the subscriber on the handset or the like to a level lower than a predetermined value If a signal pause or signal interruption is detected, a signal pause identification signal P is transmitted in the A field, ie the signaling channel of the time slot. The base station recognizes the signal pause identification signal P in the A field and interrupts decoding, amplification and / or forwarding of the signals received in the B-field Since the signaling data in the A-field are protected against transmission errors by an error correction coding (CRC), the signal pause identification signal can be transmitted reliably not forwarded by the base station and are therefore not audible on the receiving device. The transmission quality of the DECT cordless telephone system according to the invention is therefore improved.

Claims

claims 1. A method for radio transmission between a transmitting device (BS, MT) and a receiving device (MT, BS), with a user channel (B field) for transmitting voice and / or data signals and one with for transmitting signaling data Error-correcting signaling channel (A field) is provided, characterized in that when a signal pause is detected by the transmitting device (BS, MT), a signal pause identification signal (P) is transmitted to the receiving device (MT, BS) via the signaling channel, whereupon the receiving device (MT, BS) while the signal pause identification signal (P) is being received, the signals received in the useful channel are not further processed. 2. The method according to claim 1, characterized in that the signals received at the receiving device (MT, BS) during reception of the signal pause identification signal in the useful channel are not decoded and / or amplified. 3. The method according to claim 1 or 2, characterized in that the transmitting device (BS, MT) and receiving device (MT, BS) are cordless phones according to the DECT standard. 4. Cordless telephone for use in a telephone system in which a user channel (B field) is provided for the transmission of voice and / or data signals and a signaling channel (A field) provided with error correction characters is provided for the transmission of signaling data, characterized in that that the cordless telephone (BS, MT) has a device for detecting a signal pause and a device (ZST, SVE, FKT, ANT) for transmitting a signal pause identification signal (P) when a signal pause is detected. 5. Cordless phone according to claim 4, characterized in that the cordless phone (BS, MT) is a digital cordless phone according to the DECT standard.