Arrangement for controling a transmitting/receiving device of base stations and/or mobile units, in particular of a cordless telephone system

Arrangement for controlllng a transmittlng/receiving device of base stations and/or mobile units, in particular of a cordless telephone system.

The invention relates to an arrangement for controlling a transmitting/receiving devlce of base statlons and/or mobile units in particular of a cordless telephone system, according to the precharacterizing clause of patent claim 1.

Cordless telephone systems, for example systems based on the TDMA principle (Tlme _ivlsion Multlple _ccess) (for example DECT cordless system, CT2 cordless system etc.) and systems based on the CDMA principle (Code Division Multiple Access), may be designed in such a way that voice to be transmitted is compressed on the transmission side, is transmltted by the transmitting device of the transmittlng unit (base station, mobile unlt) within a radio link, is received by the receiving device of the receiving unit (mobile unit, base station) and is expanded (burst technique).

GB-A-2 249 922 discloses, for example, a mobile TDMA radio telecommunication system which has the characteristics mentioned above.

The obiect on which the invention is based consists in operating base stations and/or mobile units, in particular of a cordless telephone system, with the lowest possible use of energy.

In accordance with the present invention there is provided an arrangement for controlling a transmittlng/ A 20365-3467 ~ ~ ~ 4~ ~2 - la receivlng device of base statlons (FT) and/or mobile units (PT), in particular of a cordless telephone system, each of the base stations (FT) and the moblle unlts (PT) having a processor (M-CT), to which a controlling program (CP) is assigned and voice to be transmitted being compressed on a transmission side, transmitted by a transmitting device (RE-T) of a transmitting unit (FT, PT) within a radio link and recelved by a receiving device (RE-R~ of a receiving unit (PT, FT) and expanded, characterized ln that the controlling program (CP) activates the transmitting device (RE-T) of the transmitting unit (FT, PT) essentially only during fixed, predetermined transmission times (SZ) wlthin a transmisslon tlme frame (TDMA frame) and the receiving device (RE-R) of the recelving unlt (PT, FT) is activated essentially only during fixed, predetermined reception times (EZ) within a transmission time frame (TDMA frame), the modules re~uired for the monitoring of a frame clock being excepted from the timerelated activation.

In the case of base stations and/or mobile units, in particular a cordless telephone system, in order to reduce the use of energy required for the operation of the base station and/or of the mobile unlt wlth the exception of the modules necessary for frame-clock monitoring (e.g. in a transmlttlng/ receiving device of the base station and/or of the mobile unit) - in particular whenever the said 20365-3467 21~2~2 devices are supplied stationarily, for example via a battery, the transmitting/receiving device is switched on with a certain time lead with respect to the transmission/reception burst (Figure 4) occurring at periodic time intervals in the transmission technique (for example TDMA or CDMA methods). The lead time may in this ca~e comprise a first part-lead time (claim 2) and a ~econd part-lead time (claim 3), the first part-lead time being understood as mean;ng the r~nn;ng up time required by the electronic components of the transmitting/receiving device from the swit~h;ng-on instant to the beg;nn;ng Of the transmission/reception burst and the second part-lead time being understood a8 me~n;ng the time which ensures that the transmitting/receiving device is activated during the transmission/reception burst. In order that the transmitting/roceiving device is also switched on over the entire duration of the transmission/reception burst, the transmitting/receiving device is switched off with the end of the transmission/reception burst. In this case, as with the swit~h;ng on of the transmitting/receiving device - in analogy with the second part-lead time provided there - it i~ also pos~ible to provide a corre~pon~ing part-lag time (claim 4) for the switching off of the transmitting/receiving device, in order to ensure that the transmitting/receiving device is also switched on during the entire duration of the transmission/reception burst.

Advantageous further developments of the invention are specified in the subclaims.

According to claim 5, the transmitting/roceiving device contains on the one hand a plurality of subdevices (central functions), such as for example ~witrh;ng device~, an amplifier and an interface, and on the other hand a transmitter and receiver, which are switchod on and off simultaneously according to claim 6 and at different time~ according to claim 7.

An exG~lary embodiment of the invention is described with reference to the drawings, in which:' 214~2~2 -- 3 Figure 1 show~ an arrangement for controlling a tran~mitting/receiving device in a base station or a mobile unit of a cordless telerhn~e system, Figure 2 shows the basic construction of the transmitting/receiving device according to Figure 1, Figure 3 shows a TDMA time frame in a cordle~s tel~p system in accordance with the DECT stan~-rd, Figure 4 shows the time relationship between transmission and reception burst and the activation of the transmitting/receiving device according to Figure~ 1 and 2.

Figure 1 shows the basic circuitry of a basestation FT or of a mobile unit PT of a cordless tel~phone system. Both the base station FT and the mobile unit PT contain a radio element RE - in the following al~o referred to as transmitting/receiving device RE-T, RE-R -, a controlling element CE and peripheral elements PE, which are combined in the "peripheral elements n functional block. In the following description, it is assumed that for the cordless telephone system the DECT stan~ard (Digital European Cordless Telecommunication) is implemented.

However, the invention is not restricted to this.

For in~tance, the invention can also be readily used for comparable stan~-rds, such as for example the CT2 or GSM stanAard.

While base station FT and mobile unit PT do not differ with respect to the controlling element CE and the radio element RE or the transmitting/receiving device RE-T, RE-R - to the extent to which consideration is relevant for the invention -, the peripheral element~ PE of the base station FT and of the mobile unit PT are differently designed.

~ 4 ~ 2148282 _ For instance, the peripheral elements PE in the case of the base station FT - on the basis of base stations of known cordless telepho~ systems (Wolf, Rlaus: "Auch ohne Schnur "auf Drahtnn t~Reeping in touch" even without a cordl, Telcom Report 10, 1987, Issue 2, pages 130 et seq., for example page 134) - comprise for example internal subscriber circuits or e~ch-nge or PBX circuits with upstream ADPCM encoding/~ecoA;ng devices and an internal peripheral controller, while in the peripheral elements PE of the mobile unit PT - on the basis of mobile units of known cordless telerhone systems (Telcom Report 10, 1987, Issue 2, page 135) - there are cont~; n~A for example a microphone, a piezo receiver capsule, a piezo ringer, a storage battery, a ~eypad, an LED display, and also VF and ringer amplifiers.

The abovementioned peripheral elements PE of the base etation FT and of the mobile unit PT may also be substituted by other elements without in any way restricting the invention.

The elements of the circuitry of the base station FT and of the mobile unit PT according to Figure l which are relevant for the invention are the radio element RE or the transmitting/receiving device RE-T, RE-R and the controlling element CE.

Assigned in this case to the radio element RE, for the transmission and reception of radio signals (for example TDMA or CDMA radio signals) are two antennas A1, A2, which act both as a transmitting and a receiving antenna. Alternatively, however, it is also possible without in any way restricting the invention to assign one antenna or more than two antennas to the radio element RE.

The radio element RE has furthermore - as represented in Figure 1 by three functional blocks - a transceiver T, R, a field strength measuring device (Radio Signal Strength Indicator) RSSI and an interface RE-I, which are intercQnnscted in the radio element RE in the way represented. The field strength measuring device RSSI measures the field strength of the radio signals ~ 5 -21482~2 seleeted via the antennas A1, A2 and in the transeeiver T, R.

How the transeei~er T, R is speeifically constructed and eonneeted to the field strength measuring device RSSI and to the interfaee RE-I is shown and deseribed with referenee to Figure 2.

The field strength measuring device RSSI serves in general for testing whether a channel is loaded (cf.

DECT Draft prETS 300 175-3: 1991, page 164). The speeification as to how the field strength is to be measuredi8 given in the DECT stan~ard (cf. DECT Draft prETS 300 175-2: 1991, page 31, 6.2 and page 38, 8.3). The rhannel 10A~; n~ is in this ease established by measuring the field strength (minimum field strength) of reeeived radio signals, the measurement results RSSI1, ... subsequently being fed via an analog/digital eonverter A/D to a threshold value generator (THreshold Value _enerator) THVG, integrated in a main processor N-CT of the controlling element CE. The threshold value generator THVG in this ease forms during rllnn; n~ operation of the base station FT or of the mobile unit PT eonttn~ally updated values, which are incorporated by the main proeessor M-CT in a eontrolling plGy.am CP and eerve for driving the antennas A1, A2. With the information reeeived from the threshold value generator L~vG on the ~ann~l lo~;n~ (input variable), controlling data CDATA are formed by the eontrolling ~Gy.am CP and are fed via a main proeessor interfaee M-CTI to a subproeessor (sub-eontroller) S-CT.

The subprocessor S-CT is referred to in the base station FT as a time switch eontroller and in the mobile unit PT as a burst mode eontroller.

Assigned to the subproeessor S-CT is, inter alia, a multiplex/demultiplex unit Mn~/DEM, whieh generates or reeeives 1.152 Nbit/s data in the DECT burst format. In addition, the subproeessor S-CT assumes eontrolling funetions for the radio element RE and the peripheral elements 6 2148~)2 PE. In the ease of the base station FT, the multiplex/ demultiplex unit MUL/DEM of the subprocessor S-CT assigns to the data paekets received or to be ~ent, for ex-~ple, up to six internal or three external telepho~e eonneetions in the time division multiple access TDMA method orin the code division multiple aceess CDMA method. In addition, the subproeessor S-CT eontains a timer/eounter TI/C0, whieh supplies eloc~ pulses to the subprocessor S-CT, in particular wit_ respect to the timing of bits, time slots and TDMA or CDMA frames.

Figure 2 shows the detailed structure of the radio element RE with respect to the transeeiver T, R.

The transceiver T, R contain~ funetional bloeks whieh are independent of and dependent on the tran~mission direetions, a transmitting direetion SR and reeeivingdirection ER.

Belonging to the independent functional blocks are two 8witch; ng elements eonneeted upstream in the stated sequence of the antennas Al, A2, a change-over switeh (Diversity Switeh) DS and a seleetion switeh (T/R switch) T/R-S, switching back and forth between the transmitting direction SR and receiving direction ER.

The functional blocks of the transceiver T, R which are dependent on the respective transmiseion direction are formed, in the transmitting direction SR in the stated sequenee, by two modules eonnected between the interface RE-I of the radio element RE and the selection switch T/R-S, a synthesizer/modulator SY/M0 - also referred to in the following as transmitter - and a power amplifier PA and, in the recei~ing direction ER, by a receiver REC, connected between the field strength measuring device RSSI and the selection switch T/R-S.

21'182~2 With the exception of the change-over switch DS, all the other modules or functional blocks of the transceiver T, R are also cont~ine~ in the latter even if the radio element RE is assigned, for example, only one antenna.

The mode of operation of the cordless telecommunication in a cordless telecommunication system having the base station FT and the mobile unit PT according to Figures 1 and 2 is indicated in principle by the already mentioned printed publications (Telcom Report 10, 1987, Issue 2, pages 130 et seq. and DECT Draft prETS 175-3: 1991, entire document). Thus, in the cordles~ telecommunication system with a bidirectional (transmitter/receiver or receiver/transmitter) radio lin~ between the base station FT and the mobile unit PT, voice is on the one hand compressed and transmitted on the transmission side and on the other hand is received and eYr~n~e~ on the reception side. In order to reduce the expenditure of energy required for this in the base station FT and the mobile unit PT, in particular~Thonever the base station FT and the mobile unit PT are supplied with energy stationarily (for example by a battery or a storage battery), the transmitting device RE-T of the base station FT and of the mobile unit PT are activated essentially only at transmission times and the receiving device RE-R of the base station FT and of the mobile unit PT is activated essentially only at reception times (Figure 4).

Figure 3 shows a DECT-specific TDNA time frame for cordless telerhone systoms in accordance with the DECT st~n~rd, as is represented in German Utility Nodels G 92 14 885 (Figure 3 therein) and G 92 14 899 (Figure 2 therein).

For the cordless communication in accordance with the DECT st~n~Ard, a dynamic ~h~nn~l selection is carried out from about 120 available rh~nn~ls.

The 120 rhannels result from the fact that, in the case of the DECT st~n~rd, ten freguency bands between 1.8 and 1.9 GHz are used, operating in each frequency band according to the representation in Figure 3 in a time 2148282 - 7a _,~ division multiple access (TDMA) with a time division multiplex frame of 10 ms. In this time division multiplex frame 24 (from O 21~8282 ~ - 8 ~ _.

to 23) time r~ann~ls are defined and, as a result, a frame pattern is prescribed. This frame pattern is then used in such a way that, for each froquency band, for example 12 mobile units PT can operate simultaneously with a base station FT of a DECT communication system in duplex mode (PT-FT and FT-PT or FT-PT and PT-FT). In thie case, a time slot of respectively 417 ~8 iB assigned to the 24 time c~-nnol 8. This time slot indicates the time in which the information (data) is transmitted.

This transmission of information in duplex mode is also referred to as the ping-pong method, because transmission takes place at a certain instant and receiving takes place at another instant. In the case of this ping-pong method, in each time slot a time frame or pulse (burst) of 365 ~8, which corresponds a~G~imately to a frame length of 420 bits, is transmitted with a data throughput of 42 kbit/s. Referred to the time division multiplex frame, and bearing in mind that in a guard space GS at both ends of the time frame there are in each case 30 bits available for avoiding overlaps caused by adjacent time slots, a total data throughput of 1.152 Mbit/s is obta;n~.

On the basis of the descriptions given above with respect to Figure 3, in Figure 4 there is represented a TDMA time frame (10 ms) in which a transmission burst SB occurs with a transmission time SZ and, 5 ms later, a reception burst EB occurs with a reception time EZ (duplex mode). Thus, for example, the mobile unit PT can tran~mit in$ormation to the base station FT during the transmission time SZ of the transmission burst SB and can receive information from the base station FT during the reception time EZ of the reception burst EB (case I).

Alternatively to this, it is also possible that the base station FT transmits information to the mobile unit PT during the transmission time SZ of the transmission burst SB and receives information from the mobile unit PT during the reception time EZ of the reception burst EB (case II).

214~2~2 g , . , Since the time sequence of the transmission burst SB and reception bur~t EB is l~n~hangeably prescribed in a TDMA frame in accordance with the DECT stan~a~d (5 ms) and this time relationship between the transmi~sion burst SB and reception burst EB represent~ the time reference variable for the cordle~s operation of the base station FT and of the mobile unit PT, the base ~tation FT and the mobile unit PT are corresr~n~;ngly clock-controlled by the timer/counter TI/CO according to Figure 1 and consequently set to the DECT-specific time frame.

If the user at the mobile unit PT then wishes, for example, to transmit information in the TDNA frame (for example voice mes~ages) to the base station FT, the mobile unit PT must be ready to send at the start of transmission (beg;nn~ng of the transmission burst SB with the transmi~ion time SZ) UESP. ~Ready to send" in this case means that the radio element RE, the controlling element PT and the peripheral elements PE of the mobile unit PT according to Figure 1 are switched on. This can be achieved, for example, by the said elements being switched on for the entire duration in which the mobile unit PT is put into operation by the user. This ha~ the con~equence, however, that on the other hand the energy ~upply ~ource~ of the mobile unit PT (for example battery or storage battery) are loaded to a greater extent (in the sen~e of energy consumption) and consequently the effective operating duration of the mobile unit PT up to a battery change or charging of the ~torage battery is reduced.

In order to cater for these two requirements on the m~hile unit PT, at least partially, the tranQm;tting/ recei~ing device RE/T, RE/R is activated a_sent;ally only during the transm;~ n time SZ of the tran~m;~sion bur~t SB.

For this activation, the transmitting/receiving device RE-T, RE-R is switched on with a first lead time tvl with a_~ct to the start of tran ; R~; ~n UESP. This first lead time tvl Al 1~_~ for the fact that the tranRm;tting/receiving device RE-T, RE-R requires a certain r~nn;ng up time in order to be fully funct;~n~l (r~nn;ng up phase). The first lead time 21~282 - 10 tvl is in this case dimensioned ~uch that the ~lnn; ng up phase of the transmitting/receiving device RE-T, RE-R is ended at the start of transmission ~ESP.

H~eve , for the eventuality that the r~nn;ng up phase of the transmitting/receiving device RE-T, RE-R is not ended at the start of transmission ~ESP (for example on account of aging of the electronic components in the mobile unit PT etc.), it may be ~Ype~;ent to provide a second lead time tv2. With this second lead time tv2, it is ensured that the transmitting/rsceiving device RE-T, RE-R is in any event ready to operate at the start of transmission UESP (r~nn;ng up phase in any event ended).

The switch;ng-on instant of the transmitting/receiving device RE-T, RE-R of the mobile unit PT required for information transmission may conseguently be determined by the first lead time tvl, the second lead time tv2 or by the total lead time tvl + tv2.

In the caee of tho representation in Figure 4, it is assumed that the transmitting/receiving device RE-T, RE-R, which comprises, as described above, on the one hand the field strength measuring device RSSI, the interface RE-I, the change-over switch DS, the selection switch T/R-S and the power amplifier PA - referred to in the following as central functional elements of the transmitting/receiving device RE-T, RE-R - and also on the other hand the transmitter SY/M0 and receiver REC, iB always switched on simultaneously at the possible switching-on instants.

Alternatively, however, it is also possible that the central functional elements of the transmitting/ receiving devices RE-T, RE-R are switched on at different times than ths transmittor SY/M0 and the receiver REC.

In addition, it is also conceivable to ~Yran~ the transmission time-related switch;ng-on of the mobile unit PT to all the functional modules - 11 21~1828~ ' of the mobile unit PT which are not required for the monitoring of the TDMA frame clock.

In analogy with the second lead time tv2, it iB possible furthermore to define a lag time tn2, with which the transmitting/receiving device RE-T, RE-R is switched off with respect to an end of transmission (end of the transmission time SZ of the transmission burst SB) ~EEP.

This achieves the effect that the transmitting/receiving device RE-T, RE-R is not switched off too early in the possible event of a time/frequency drift of the timer/ counter TI/C0.

The descriptions given above with respect to the transmission burst SB with the transmission time SZ are applicable in a similar way also to the reception burst EB with the reception time EZ, in which the mobile unit PT receives information (for example voice messages) from the base station FT. In addition, the said descriptions of the transmitting/receiving mode of the mobile unit PT within a TDNA frame (case I) are applicable in the same way to the transmitting/receiving ~ de of the base station FT within a TDMA frame according to Figure 3 (ca~e II).