KR100561930B1 - Time-division multiple accesstdma multi-line wireless telephone system, communication method thereof and wireless handset - Google Patents

Abstract

The wireless telephone system includes a base unit connectable to one or more external telephone lines and having a base transceiver and a plurality of wireless telephone handsets that can be activated or deactivated. Each handset has a handset transceiver to establish a time-division multiple access (TDMA) link when the handset is activated over a shared RF channel with the base unit via a base transceiver. In communication over TDMA, each active handset communicates during an exclusive time slice of the TDMA structure, which allocates a time slice to the active handset, and multiple data samples having a sample size are transmitted during each time slice. At least two handsets alternately share time slices when one of the two handsets establishes a new TDMA link and when establishing a new TDMA link exceeds the effective channel capacity. The time slice is shared by reducing the sample size to increase the number of data samples transmitted during the shared time slice.

Description

TIME-DIVISION MULTIPLE ACCESS (TDMA) MULTI-LINE WIRELESS TELEPHONE SYSTEM, COMMUNICATION METHOD THEREOF AND WIRELESS HANDSET}

The present invention relates to a multi-line wireless telephone system.

The use of telephones and telephone systems, including wireless telephone systems, is becoming popular. In a cordless telephone system, a cordless or cordless telephone handset unit communicates with the base unit via an analog radio signal or a digital radio signal, which is generally connected to an external telephone network via a standard telephone line. In this way, a user can use a wireless handset to make a phone call with another user through the base unit and the telephone network.

Multi-line wireless telephone systems are also used in many situations, such as doing business with many telephone users. Such systems typically use handsets that communicate with up to N handsets simultaneously, through digital communication structures such as time division multiple access (TDMA). It is desirable to implement the characteristics of the current Private Branch Exchange (PBX) system in a multi-line wireless telephone system. Conventional multiline radiotelephone systems generally must operate with a specific bandwidth and modulation format, so this characteristic of the radio-frequency (RF) channel used to transmit signals between the base unit and an active or active handset. Limit the maximum dose.

One problem arising from the fixed capacity available to such telephone systems, i.e. bandwidth and the inflexibility of such systems, is that the available channel capacity can be used inefficiently when not all handsets are operating. This is because in some such systems, for example as disclosed in the European patent application (No. 0 587 225 A2), the channel capacity is chosen to allow all N handsets to operate simultaneously when needed. However, when less than N handsets are operating, channel capacity is insufficiently used. The overall signal quality can be reduced to also reduce the total bandwidth (and thus the amount wasted when not all the handsets are used), but this is one example to ensure that only one handset is operating and this single handset is communicating at high quality. Unnecessarily degraded in some cases where there is sufficient total channel capacity available.

The wireless telephone system includes a base unit that can be connected to one or more external telephone lines and has a base transceiver and a plurality of wireless handsets that can be activated or deactivated. Each handset has a handset transceiver for establishing a time-division multiple access (TDMA) link over a shared RF channel with the base unit via the base transceiver when the handset is activated. In a communication over a TDMA link, each active handset communicates during an exclusive time slice of a TDMA structure that allocates a time slice to the active handset, wherein a plurality of data samples having a sample size are each timed. Sent during the slice. When one of the at least two handsets establishes a new TDMA link and when the setting of this new TDMA link exceeds the available channel capacity, the at least two handsets alternately share time slices. The time slice is shared by reducing the sample size, thus increasing the number of data samples transmitted during the shared time slice.

1 is a block diagram illustrating a TDMA multiline wireless telephone system, in accordance with an embodiment of the present invention.

FIG. 2 is a schematic representation of the field, data packet, and audio packet structures used in the TDMA structure of the system in FIG. 1; FIG.

3 is a table illustrating a variable-structured TDMA time slice allocation structure used in the system of FIG. 1, in accordance with an embodiment of the present invention.

4 is a table illustrating a fixed-structure TDMA time slice allocation structure used in the system of FIG. 1, in accordance with an embodiment of the present invention.

Referring now to FIG. 1, shown is a block diagram of a TDMA multiline wireless telephone system 100 in accordance with an embodiment of the present invention. The TDMA system 100 includes a base unit 110 having a receiver unit 112 and a transmitter unit 111, respectively, and connected to an external telephone network 116 via telephone line (s) 115. The base unit 110 also includes a controlled microprocessor 113 for controlling and monitoring the overall functionality of the base unit 110. System 100 also includes N wireless handsets 120 ₁ , 120 ₂ ,... 120 _N. Each handset has a transceiver unit (transceiver), such as transmitter 121 and receiver 122 of handset 120 ₁ . In one embodiment, receiver unit 112 includes N individual logic receivers, and transmitter unit 111 includes N individual logic transmitters, so that receiver unit 112 and transmitter unit 111 comprise N wireless radios. A total of N logical transceiver units will be provided, one for each handset. At any given time, M handsets 0 < = M < / RTI > N are in operation (i.e. in the process of conducting a phone call). Since handsets are generally battery-powered, efficient power usage is important for wireless systems. Therefore, in one embodiment, the system 100 uses a digital TDMA structure, as will be described in more detail later, wherein the TDMA structure is " off " most of the time at which each operating handset is operating (i.e., No data is transmitted or received), so that it is only "on" during its own "time slice" or slot so that power is used efficiently. Thus, system 100 provides a wireless network between base station 110 and each handset 120 _i (1 ≦ _i ≦ N).

In the present invention, a TDMA structure is used in which the available channel capacity is used more efficiently. This is accomplished by reducing the quality of two or more handset signals and alternating the signals with each different time slice when a certain number of handsets are in operation, as described in more detail below with reference to FIGS. .

Referring now to FIG. 2, a schematic diagram 200 of the field, data packet, and audio packet structure used in the TDMA structure of the TDMA system 100 in FIG. 1 is shown. In one embodiment, zero digital data field 210 includes a total of nine packets, that is, eight audio packets, such as one data packet 220 and audio packet 230. Each data packet is transmitted from a base unit to a given handset or vice versa over discrete time slices during times when other handsets do not receive or transmit data over the system's data channel. Data set. Each audio packet is transmitted from the base unit to a given handset during a given time-slice in the overall " epoch " structure, and during times when no other handset receives or transmits data over the system's data channel. Or vice versa.

As shown, each type of packet includes several sub-fields or sections. In one example, the data packet 220 may include a 32-bit sync field 224, a data field 225, a forward error correction (FEC) field 222, and a guard time 223. Include. The data in data packet 220 is used to communicate between the base unit and a particular handset and includes various types of information such as caller ID type information, range and power information, and the like.

The audio packet 230 includes an audio packet header 231, an FEC data section 232, and a guard time 233. The audio packet header 231 includes information for identifying an audio packet (such as a handset), a current position in the period, and the like, for example.

In normal operation, each handset has 16 digitally compressed audio samples {ADPCM (adaptive differential pulse code modulation) during each time slice of the period allocated for the handset to receive audio data. Receive a sample, such as a sample, and send 16 ADPCM samples to the base unit during each time slice of the time period allocated for the handset to transmit audio data. However, in the present invention, when too many handsets are operating relative to the transmission channel capacity, the handset pair alternates its use and doubles the number of samples to 32 per time slice (by reducing the quality of each sample). ) Share time slices. ADPCM and related technical issues can be found in the adaptive differential pulse code modulation (ADPCM) implemented with "5-, 4-, 3- and 2-bit samples" in Recommendation G.727 (12/1990) of the International Telecommunication Union (ITU). ) "(Http://www.itu.ch).

Thus, audio packet 230 may also contain a major 64-bit "audio data" portion, which may include 16 4-bit ADPCM samples (high quality) or 32 2-bit ADPCM samples (low quality). . An audio packet containing 32 two-bit ADPCM samples corresponds to the case where more handsets are operating than the number of handsets capable of operating at high quality through the allocated maximum channel capacity of the system 100. Thus, in the present invention, each handset in operation operates at a higher quality when fewer handsets are active (in a call) than T handsets, where M < T and the maximum channel capacity is up to T. It is enough to handle high quality calls or links simultaneously. However, when more than T handsets are in operation (M> T), the selected handset channel pair switches from the high quality audio link to the low quality audio link and alternates the time slices. As will be appreciated, for the 2 ms field, high quality (16 4-bit ADPCM samples per audio packet or time slice) provides 32 Kbps ADPCM (default audio data) and low quality (between two handsets per audio packet). (32 32-bit samples shared by) provide 16 Kbps.

Therefore, in a limited way, this embodiment of the invention allows the high quality maximum handset capacity to be doubled at low quality. In one embodiment of the system 100, up to four handsets can simultaneously make calls with high quality, and up to eight handsets can make calls with low quality. For the intermediate number, each additional handset added to the previous four handsets must be paired with one of the first four handsets (eg, if M = 7, three handsets in addition to the first four handsets Is present, so 3 out of 7 handsets of 6 handsets operate at low quality).

Referring now to FIG. 3, in accordance with an embodiment of the present invention, a variable-structure TDMA time slice allocation scheme epoch used by system 100 in FIG. 1 is described. Table 300 is shown. Table 300 includes N pairs of rows, each of which is for an existing handset. Each row is a field such as field 210 of FIG. In the variable configuration of table 300, N may be greater than eight. In one example, N may be 12. Each row of the period or field of the epoch may be referred to herein as an initial time slice, or slot, which transmits data TD to a given handset or receives data RD from a given handset. Can be used for Thus, at the beginning of the field, data is transmitted (or received) from the particular handset. Thus, as an example, base unit 110 transmits data to handset # 1 (eg, handset 120 ₁ of FIG. 1) in the first time slice of row TD1; Base unit 110 then receives data from handset # 1 in the first time slice of row RD1. As such, each handset receives and transmits data during one time slice of the entire Q slice period, where Q = 9 × 2 × N. Thus, although any number N of handsets can be added, the time delay for data communication between a given handset 120 _i and the base unit 110 can therefore be long. This may, for example, result in longer time delays or latency to make certain handsets ring or know caller ID information.

In operation, certain handsets poll at specific data channel slots to accept call and sync data from base unit 110 and transmit audio packets during specific data channel time slots when initiating a call. Audio packet pairs (e.g. TS1, RS1) in each field 210 (each row in table 300) can send one conversation using 32 Kbps ADPCM or two using 16 Kbps ADPCM. Two calls may be sent (see ITU Rec. G. 727). In this embodiment, sixteen 4-bit samples are sent in each direction to the handset every 2 ms. Table 300 shows a time sequence of left to right, top to bottom, horizontally 2 ms, and vertically 2 × 2 × N ms (32 ms when N = 8).

In one embodiment, the system 100 implements the period of the table 300 as follows. The channel capacity of the system 100 is sufficient to operate up to T = 4 handsets with high quality. Thus, for the first four handsets to operate, the four handsets are assigned nominal numbers 1 to 4. As each time slice of table 300 cycles through (left to right, top to bottom), use the assignment shown as the top entry in the two rinsed TD rows of the pairs of rows, that is, not in parentheses. Thus, we have the following sequence:

TD1, TS1, RS1, TS2, RS2, TS3, RS3, TS4, RS4;

RD1, TS1, RS1, TS2, RS2, TS3, RS3, TS4, RS4;

TD2, TS1, RS1, TS2, RS2, ...

...

RDN, TS1, RS1, TS2, RS2, TS3, RS3, TS4, RS4;

Where "TS1" represents the time slice during which an audio signal or "sound" packet is transmitted to the handset # 1 through the base unit 110; And "RS1" indicates a time slice while an audio packet is received from handset # 1 through base unit 110; This continues.

However, each audio packet time slice entry of the table 300 includes two entries. When M ≦ T, the top entry of the TD row or field indicates the “normal” allocation of slots for both the TD and RD rows. This assignment is used for both TD and RD rows, which are pairs of rows. As an example, if only four handsets are active (off hook), then the sequence described above follows, i.e. both the TD and RD rows follow the sequence indicated by the top entry in the TD row.

The lower entry in parentheses indicates the alternate allocation for the slot when M> T. The top entry represents the normal shift assignment when M> T. If the fifth handset (handset # 5) is operational, there is not enough channel capacity to process all five active or active handsets with high quality. Therefore, handset 1 and handset 5 share a time slice in the alternating field, and each audio packet is twice the number of samples transmitted during the time slice. As an example, in this case, during the first audio packet time slice of row TD1, entry TS1 indicates that 32 2-bit audio ADPCM samples are sent to handset # 1 instead of the usual 16 4-bit samples. Indicates. During the first audio packet time slice of row RD1, entry TS5 indicates that 32 two-bit audio ADPCM samples are sent to handset # 5 during this time slice. Providing 32 two-bit ADPCM samples in the audio packet for handset 1 provides sufficient audio data for a 4 ms TDMA cycle. The system is dynamic because if handset # 1 is disconnected before handset # 5, base unit 110 can allocate 32 Kbps to handset # 5 for the remainder of the call. Depending on when handset # 5 is active, the order may be switched so that the entries in parentheses become applicable.

Therefore, when M> T, it can be said that the system 100 operates in the handset extension mode. In normal mode, a total of 32 4-bit samples are sent to handset # 1 every two fields (ie, high quality TS1 occurs twice). In the handset extension mode, 32 2-bit (low quality) samples are also sent to handset # 1 every two fields, except that in one audio packet rather than two audio packets. When additional handsets beyond the first four handsets are activated, the system 100 dynamically switches to handset extension mode and nominally numbers the newly activated handsets, which, as described, is a time slice of the other handset. Paired as described by. Thus, as an example, if handset # 6 is active, handset # 6 alternately shares time slice (and low quality) with handset # 2. In this case we have:

TD1, TS1, ^* RS1, ^* TS2, ^* RS2, ^* TS3, RS3, TS4, RS4;

RD1, TS5, ^* RS5, ^* TS6, ^* RS6, ^* TS3, RS3, TS4, RS4;

TD2, TS1, ^* RS1, ^* TS2, ^* RS2, ^* TS3, RS3, ...

...

RDN, TS5, ^* RS5, ^* TS6, ^* RS6, ^* TS3, RS3, TS4, RS4

Where * denotes a low-quality audio packet (ie, 2-bit sample).

Thus, base unit 110 assigns transmit and receive slots to each subsequent active handset for audio transmission. If no handset is in use, handset 120 ₂ initiates the call, and transmit slot TS1 and receive slot RS1 are assigned to handset 120 ₂ (ie, handset # 1) at a rate of 32 Kbps. Will be. Thus, for up to four active handsets, a high quality audio link of 32 Kbps is provided for each handset. When the fifth handset is activated, one existing channel is reduced to 16 Kbps and the fifth handset is multiplexed to that channel at 16 Kbps. If more than eight handsets attempt to transmit, the handsets are blocked (all lines are in a call signal state). In such embodiments where blocking is possible, receiver unit 112 preferably comprises fewer than N individual transmitters (preferably 8), and transmitter unit 111 preferably contains fewer than N individual transmitters (preferably 8). Dogs). In general, in some embodiments base unit 110 includes as many logical transceiver pairs as the maximum number of calls (links) that can be established simultaneously.

Thus, in the epoch of table 300, in normal mode each active handset has a fixed time slot (i.e. row of table 300) for each field 210 for audio data delivery. In the extended handset mode, low quality handsets have a fixed time slot (i.e., row of table 300) for every other field 210 for audio data delivery.

In one embodiment, the system 100 is modified to dynamically reassign handsets to optimize the use of channel capacity. As an example, suppose six handsets are operating as described above, and four of the six handsets operate in a low-quality mode. Next, assume that handset # 3 and handset # 4 are inactive. In this case, it makes no sense that handset # 1 and handset # 5 share a time slice or operate in a low quality mode because the time slices for TS3, RS3, TS4, RS4 are not in use. Thus, in this case the system 100 dynamically renumbers or renumbers four running handsets # 1- # 4.

Thus, in the present invention, TDMA is used to separate data and audio into two channels and to allocate bandwidth when required by the handset that needs the channel. This technique is compatible with power-saving protocols because a data channel that is always available is used to signal the handset and initiate the call. A specific time slot is provided with data for each handset, which is used to keep the TDMA in sync so that the handset transceiver only communicates for a specified time slice. Because the phone is battery powered, it is important to only send and receive when the phone is needed.

In one embodiment, system 100 is based on the telephone system having four plain old telephone system (POTS) lines (i.e., lines 115), and the epoch and structure of table 300. Implement With four dedicated POTS lines, users can always expect performance of 32 Kbps, except when several handsets are in a meeting or when some handsets are on an internal call and at the same time other handsets are on the line. In alternative embodiments, other line / handset combinations may be used.

In the above embodiment, two transmit / receive pairs are used per audio data packet slot. In alternative embodiments, smaller or larger number of transmit / receive pairs may be used per data slot. In one example, the audio data sample may be further reduced in quality to transmit more samples per audio packet, such that more than two handsets (eg, four) share a time slice. However, this may require higher compression algorithms, which will add significant delay to the loop. By using an ADPCM as described above, it is possible to minimize delays in the loop and simplify the audio echo cancellation problem, and both the 16 Kbps algorithm and the 32 Kbps algorithm exhibit the same delay to facilitate switching between the algorithms. .

Referring now to FIG. 4, shown is a fixed-structure TDMA time slice allocation structure duration used in the system 100 in FIG. 1, in accordance with an embodiment of the present invention. In this embodiment, the flexibility is further reduced by adding additional handsets beyond the channel capacity limit. However, table 400 may be implemented more simply than the variable solution of table 300, and may prevent blocking from occurring.

The epoch scheme described in table 400 may be implemented similar to the period structure of table 300 when N = 8. In one embodiment for table 400, time slots have been assigned to each handset for both data and audio. Thus, as an example, if handset # 1 and handset # 5 are the only active handsets, the handsets would each operate at 16 Kbps ADPCM, even if there is additional bandwidth or available channel capacity. However, although this may not be the most "efficient" way to use the channel, this simplifies the control of the channel. In alternative embodiments, in implementing the epoch of the table 400, the system 100 may dynamically reassign the handset number to more efficiently use the available bandwidth.

Those skilled in the art will appreciate that the wireless system described above in accordance with the principles of the present invention may be a cellular system in which the base unit 110 represents a base station that serves as one of the cells in a cellular telephone network.

It is understood by those skilled in the art that many modifications to the description, materials, and apparatus of the parts depicted and described above to illustrate the nature of the invention may be made without departing from the spirit and scope of the invention as set forth in the following claims. Will be.

Claims (19)

As a wireless telephone system, (a) a base unit 110 connectable to one or more external telephone lines and having base transceivers 111 and 112; (b) as an active or a plurality of wireless handsets (120 ₁ -120 _N) that may be inactive, when each of the wireless handset is a handset is activated, via the base transceiver over a shared RF channel with the base unit A handset transceiver for establishing a time-division multiple access (TDMA) link, wherein each active handset communicates during a time slice of a TDMA structure that allocates a time slice to the active handset, and has a plurality of data samples having a sample size A plurality of wireless telephone handsets, transmitted during each time slice, and (c) when one of the two handsets establishes a new TDMA link and when establishing the new TDMA link exceeds the available channel capacity, it is transmitted by reducing the sample size and during the shared time slice. Means 113 for increasing the number of data samples so that at least two handsets alternately share the time slice Wherein the TDMA structure includes an epoch having a plurality of pairs of transmit and receive data rows, one pair of such rows for each handset, each row comprising a data field and a specified number of And divided into time slices, each field having a length of 2 ms. 10. The system of claim 1 wherein the data sample is an adaptive differential pulse code modulation (ADPCM) sample, each ADPCM sample having a plurality of bits. The method of claim 1, wherein the plurality of handsets comprise exactly N wireless handsets, The TDMA structure includes an epoch having N transmit data rows and N receive data rows, Each active handset receives or transmits 16 4-bit ADPCM samples during each time slice for the handset when no handsets share a time slice, When the at least two handsets share a time slice for one of the two handsets, each of the two handsets receives 32 two-bit ADPCM samples during an alternately shared time slice for each of the handsets. Transmitting or transmitting, wireless telephone system. The method of claim 1, wherein the TDMA structure includes a period having a plurality of row and transmit data row pairs, wherein the row pair is for each handset, Each active handset receives data and transmits data through the data slice only once during each epoch, during the pair of transmit and receive data rows for the respective active handset. delete 10. The system of claim 1 wherein the TDMA structure is a variable TDMA structure in which the number of handsets is greater than the maximum number of links that can be established over the channel. 2. The wireless telephone system of claim 1, wherein the TDMA structure is a fixed TDMA structure equal to the maximum number of links that the number of handsets can set over the channel. The method of claim 1, wherein the plurality of handsets comprise eight handsets, Up to four handsets can be active for use without sharing the time slice, Up to eight handsets can be activated by sharing the time slice. 2. The system of claim 1, wherein the TDMA structure includes an epoch having a plurality of pairs of transmit and receive data rows, with one such pair of rows for each handset, Each handset is powered by a battery, Each active handset is on during the epoch during its own time slice, and otherwise off. In a wireless telephone system comprising a base unit 110 and a plurality of wireless handsets (120 ₁ -120 _N), and wherein the base unit comprises one or more external telephone lines connectable to the base transceivers 111 and 112, the plurality of radio A handset may be activated or deactivated, respectively, each handset comprising handset transceivers 121 and 122, wherein: (a) establishing a TDMA link with the handset transceiver of each active handset via an RF channel shared with the base unit via the base transceiver, wherein each active handset assigns a time slice to the active handset; Communicating during an exclusive time slice of the structure, establishing a TDMA link, wherein a number of data samples having any sample size are transmitted during each time slice, and (b) when one of the two handsets establishes a new TDMA link and when establishing the new TDMA link exceeds the available channel capacity, it is transmitted by reducing the sample size and during the shared time slice. Increasing the number of data samples, such that at least two handsets alternately share the time slice Wherein the TDMA structure includes an epoch having a plurality of pairs of transmit and receive data rows, with one such pair of rows for each handset, each row containing a data field and a specified number of Wherein the field is divided into time slices, each field having a length of 2 ms. 11. The method of claim 10, wherein the data sample is an adaptive differential pulse code modulation (ADPCM) sample, each ADPCM sample having a plurality of bits. 11. The method of claim 10, wherein the plurality of handsets comprise exactly N wireless handsets, The TDMA structure includes an epoch having N transmit data rows and N receive data rows, Each active handset receives or transmits sixteen 4-bit ADPCMs during each time slice for the handset when no handsets share a time slice, When at least two handsets share a time slice for one of the two handsets, each of the two handsets receives 32 two-bit ADPCM samples during an alternately shared time slice for each of the handsets, or Communication method to transmit. 11. The method of claim 10, wherein the TDMA structure includes a plurality of pairs of transmit and receive data rows, wherein the pair of rows is for each handset, Each active handset receives data and transmits data over a data slice only once during each epoch, during the pair of transmit and receive data rows for each active handset. delete 11. The method of claim 10 wherein the TDMA structure is a variable TDMA structure, wherein the number of the handsets is greater than the maximum number of links that can be established over the channel. 12. The method of claim 10, wherein the TDMA structure is a fixed TDMA structure equal to the maximum number of links that the number of handsets can set over the channel. 11. The method of claim 10, wherein the plurality of handsets comprise eight handsets, Up to four handsets can be active for use without sharing the time slice, At most eight handsets can be activated by sharing the time slice. 11. The system of claim 10, wherein the TDMA structure includes an epoch having a plurality of pairs of transmit and receive data rows, with one such pair of rows for each handset, Each handset is powered by a battery, Each active handset is on during the epoch during its own time slice and off otherwise. A wireless handset for use in a wireless telephone system having a base unit and a plurality of wireless handsets, the base unit being connectable to one or more external telephone lines and having a base transceiver, wherein the wireless handset comprises: (a) a handset receiver; (b) a handset transmitter, Each of the plurality of wireless handsets may be active or inactive, The handset receiver and handset transmitter, when the handset is activated, for establishing a time-division multiple access (TDMA) link over a shared RF channel with the base unit via the base transceiver for the handset. Provide a handset transceiver, Each other of the plurality of wireless handsets is a handset for establishing a time-division multiple access (TDMA) link over an RF channel shared by the base transceiver with the base unit when the other handset is activated. A transceiver, wherein each active handset communicates during an exclusive time slice of a TDMA structure that allocates a time slice to the active handset, a plurality of data samples having a random sample size are transmitted during each time slice, When one of at least two of the plurality of handsets establishes a new TDMA link and when establishing the new TDMA link exceeds the available channel capacity, the sample size is reduced and transmitted during the shared time slice. By increasing the number of data samples, the at least two handsets of the plurality of handsets alternately share the time slice, The TDMA structure includes an epoch with a plurality of pairs of transmit and receive data rows, for each handset, one pair of such rows, each row containing a data field and divided into a specific number of time slices. Wherein each field has a length of 2 ms.

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