CZ204997A3 - Transitions within telecommunication systems - Google Patents

Abstract

A telecommunications system, such as a wide area digital paging system, comprises a plurality of geographically separated primary stations (PS1, PS2, PS3), each defining a coverage area (CAR1, CAR2, CAR3), controlled by a system controller (10) to operate as a large area network. Subscriber units (SS1, SS2) are able to roam from coverage area to coverage area. In order for a roaming subscriber unit (SS1, SS2) to know which channel it should tune to, the primary stations (PS1, PS2, PS3) from time to time transmit a system wide announce channels message giving details of the channels available. The subscriber units have means for selecting one of the available channels.

Description

Transitions in telecommunication systems

Technical field

The present invention relates to transitions in telecommunications systems, particularly, but not exclusively, in digital paging systems.

BACKGROUND OF THE INVENTION

In the case of one operator, a single frequency paging system, a large radio coverage area is divided into several sub-areas, and the subscriber may choose one or more sub-areas in which he wants to be paginated, with a charge for each sub-area. Therefore, the subscriber knows in advance in which sub-areas he can be contacted when moving to other areas. If two or more independent operators use one channel, it may be necessary for the operator to include some form of operator identification in the paging so that a subscriber registered by one operator can distinguish a paging signal addressed to its terminal from a signal sent similarly to a subscriber unit belonging to another system. Transmitting operator identity can also be used by the pager to differentiate between networks, thus avoiding listening to the wrong network and thus saving battery power.

In some countries, frequency bands or paging channels have been allocated where competing operators are assigned one or more channels from the band. A terminal unit that • • • • • · · · · · · · · · · · · · «« «« «« · · · · · Belong to a subscriber who is within a certain area, must be able to detect the geographic channel (s) assigned to the operator and select that or these channel (s) used in each area. In addition, if a special channel is assigned to the operator, the terminal unit must be able to capture the channel whenever needed.

SUMMARY OF THE INVENTION

It is an object of the present invention to facilitate the transition of subscribers in an area covered by a telecommunications system.

One aspect of the present invention is a telecommunications system comprising a plurality of geographically remote primary stations wherein each primary station defines a coverage area, the plurality of primary stations operating as a network and at least one mobile secondary station characterized in that each primary station is adapted for transmission available channel reports containing information about available radio channels on the network to which it belongs, and in that the secondary station has the means to receive these available channel reports and to select the channels included in the message.

A second aspect of the invention is a secondary station for use in a telecommunications system comprising a plurality of geographically remote primary stations that are operated on a network, each primary station being adapted to transmit available channel reports containing radio channel information available on the network , the secondary station comprises means for receiving a signal, means for storing channel details. · · · ··················· Network belonging and means sensitive to receiving reports of available channels for selecting details about at least one of the channels contained in the means for storing and adjusting the secondary station according to the same.

Overview of the drawings

The invention will now be described by way of example with reference to the accompanying drawings, in which Fig. 1 is a block diagram of an embodiment of a digital paging system on a wide area; Fig. 2 shows an example of a cyclic structure; Fig. 5 shows an example of a sub-address code word; Fig. 6 shows an example of available channel report; Fig. 7 shows an example of four phase-offset regions; Fig. 8 is a table showing the phasing of three frequencies in adjacent regions; Fig. 10 shows an example of five phase offset regions operating on four channels, and Fig. 11 shows a sequence of frequencies used in Fig. 10.

In the figures, the same numbers have been used to refer to • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·

DETAILED DESCRIPTION OF THE INVENTION

The paging system of FIG. 1 includes a paging system controller (PSC) 10 that is connected to the PSI primary stations via terrestrial links. PS2 and PS3. that are geographically distant. Each primary station includes a transmitter that defines the coverage area CAŘI. CAR2 and CAR3. which may overlap one or more adjacent coverage areas. The PSC 10 may control the operation of the primary stations in one of several ways, for example, quasi-synchronous single-frequency, single-frequency time division, or multi-frequency. As will be apparent from the following description, one geographic area may be covered by two or more networks, each having its operator having PSC and geographically located primary stations arranged so that the areas covered by the primary stations of one network are arranged differently than the areas covered by another network .

In Fig. 1, users of secondary stations SS1, SS2. which include, for example, digital pagers, can move within a predetermined home area and are reachable in that area by the primary station. However, if, for example, the secondary station SS1 should operate in other coverage areas, then this must be recorded in the PSC 10. In addition, users may want to be reachable in other geographic areas where the network managed by other operators prevails. Each operator may have one or more channels assigned to its system and may have its operator identity and area code. Also, the modes of operation may be different for different operators, each of which may offer a different range of services, such as standard, low-speed service speeds, or one or more high-speed standards.

The secondary station SS1 is shown in a block diagram. The antenna 12 is connected to a reception stage 14. the output of which is connected to a decoder 16. The microcontroller 18 is controlled by software stored in program memory 22. The address stack 24 contains the address (s) assigned to the secondary station and is connected to The RAM 26 for storing data messages received from the primary station is coupled to the microcontroller 18. This has an output connected to the LCD driver 28. which is connected to the LCD panel 30. The keyboard 32 is connected to a microcontroller, from which a person enters commands to the device. The acoustic transducer 34 and the light source 36, e.g., LED, are coupled to the microcontroller 18. which uses them as a label and in addition, the light source 36 may be used to transmit optical messages stored in RAM 26 to a printer or personal computer. The receiver 14 is controlled by a microcontroller 18 according to the battery power saving protocol, and the battery saving stage 38 is connected between the microcontroller 18 and the receiver 14.

The additional memory 40, which may be part of the program memory 22, has several memory locations 42-52 for storing various data that has been written as part of the secondary station's program. At 42, there is channel information. At 44, a home environment identification is stored, i. operator identity and area code. This information is used by the secondary station to determine when there is coverage in its area, such as CAŘI. and when it hosts or moves to another coverage area and the appropriate addressing mechanism may be used. Site 46 contains information related to the home channel that is programmed. However, pagers will need to select the channel dynamically when switching to the same coverage area. At location 48 is the operator identity and associated area codes that are valid for the secondary station when passing outside its home area. In certain cases, the secondary station will have one programmed operator identity. However, the operator may want to use several operator identities to increase the addressing capacity. At 50, data relating to the decoding of the operator identity and the area code field contained in the particular codeword, such as a zero dose pointer used to identify the dose, will be stored, as will be explained below. At position 52, one or more channel research algorithms are usable for use in various protocols.

The present invention will be described by reference to a paging protocol in which transmission is performed in CYC cycles (Fig. 2). Each cycle contains a plurality of doses of BO, B1. B2, each batch comprises a synchronization codeword and a plurality of frames F0 to F27, and each frame comprises several periods of code 12 or 16, code words of words, e.g., rates.

6, 8, The first depending on the bit in each batch is the synchronization codeword S, and in the first batch of the BO cycle the codeword called the zero dose pointer (BZM) is the first codeword following the synchronization codeword. BZM allows the secondary station to achieve cycle and batch synchronization.

Giant. 3 shows the BZM format, which is a 32-bit codeword. Bit 1 contains a one-bit flag with a value of 0 on the batch that does not follow the address code word indication. Bit 2 is a BZM flag having a value of 0 for a BZM and a value of 1 for any other address codeword. Bits 3-15 are for operator identity (AI) and area code (AC) of the paging network. Bit 16 is used to indicate the cycle or batch operation mode, where 0 is the cycle mode. Bit 17 indicates whether a zero message follows 1 indicates that a zero dose message A zero dose message is used to transmit system messages transmitted to all pagers in the network. Bits 18-21 of BZM represent a SUM sum containing a 4-bit checksum of information in the message codeword. However, for a BZM that is not followed by a zero-dose message, the SUM field includes a two-bit string indicating the number of repetitions of cycles and a two-bit string indicating the number of repetitions. The remaining eleven bits contain a 10-bit CRC and one parity bit.

In operation, the primary station transmits a sequence of messages that have been formatted and encoded to match the format shown in FIG. 2. Since the system described is a synchronous system, transmission begins with a short preamble P, which is immediately followed by the first batch B0 of the first cycle.

The receiving stage 14 (FIG. 1) of the secondary station SS is powered to receive the preamble, and thus bit synchronization is achieved. The preamble is followed by the first son code word, and it is followed by the BZM. Assuming that the synchronous code word and the BZM have been received correctly, it is tested whether the operator identity (AI) and the area code (AC), i.e. bits 3-15 BZM, correspond to the operator home identity and the area home code that are in the secondary station. programmed. If they match, then the transmission is performed as a local transmission and the secondary station follows the battery saving protocol, which usually requires at least the receiving stage 14 to be powered from the secondary station until the beginning of the determined dose frame. During the frame period, the transmissions of the primary station are monitored to see if any successfully received codeword matches the address (s) assigned to the pager. If the message is not associated with an address code word, the secondary station receiving stage 14 is powered at the end of the frame period, and the alarm device is powered when necessary. Otherwise, the receiver remains powered until the end of the message is indicated, e.g., by an address code word or message code word, and then one or more alarm devices 34, 36 are powered when necessary.

Another possibility is that the operator identity and the area code do not match the operator home identity and the area home code, and then the secondary station knows that it is outside the home area. The primary station is also aware that it is transmitting the secondary station during the transition and transmits the transition address code word and the sub-address code word within a predetermined frame. Figures 4 and 5 show one case of each type of codeword, each 32 bits long. First, we notice the transition address codeword, where bit 1 is a flag with a value of 1 indicating the address codeword. Bits 2 through 7 are transition flags, and setting all bits to 1 sends an indication that a transition message follows. Bit 8 is reserved. Bits 9-21 indicate the operator's home identity and area code to which the secondary station is connected. Bits 22-31 are CRC and bit 32 is a parity bit.

The sub-address code word (FIG. 5) starts with a flag of value 1 indicating the code word of the message, bits 2 to 17 contain address bits corresponding to the address of the secondary station. Bits 18-21 are network string elements of a four-second checksum of information in the message codeword. Bits 22-31 contain a 10-bit CRC and bit 32 is a parity check bit. The receiving station 14 of the secondary station is powered within a predetermined frame and determines whether the operator's home identity bits match the bits stored in the secondary station and, if so, determines whether the address in the subaddress code word matches the word given to the secondary station and it is powered to receive the next message, but otherwise it is disconnected at the end of the frame.

In the present description, it has been assumed that all networks operate at one frequency. However, multi-frequency (or multi-channel) mode is also possible, in the secondary station it reprograms information regarding all available channels in the form of numbers.

Calls to a single channel secondary station are transmitted by the channel that is programmed to the pager. Calls to the multichannel secondary station in the home area of the secondary station are transmitted by the home channel of the secondary station.

To make calls to the guest multichannel secondary station, the channel selection method uses an available channel report that is continuously broadcast on all channels belonging to the operator.

Giant. 6 illustrates the command parameters in the available channel report. The message begins with parameter A, which contains the operator identity and area code. which corresponds to the same information in BZM. Parameter B specifies the name given to cover the frequency, channel • (or paging) area. The P parameter is a single digit that defines the cycle phase in a specific area, as will be explained later. Digits can have the following values and meanings:

phase T phase T + phase T ++ undefined phase

Parameter D refers to a period without transmission, and is a number defining the period of transmission of a certain operator in a certain area.

indefinite period

The secondary station will use pre-programmed values or default values if nothing is programmed.

up to 32 period without transmission

The Q parameter is an integer that indicates the number of radio channels that are operating on a particular paging area and that are specified in the following list. Finally, each of the parameters c0, c1-cQ-1 includes a number indicating the radio channel that is in operation in a particular paging region.

The available channel report is typically transmitted in a zero dose report and informs the pagers about the available radio channels in a particular network in a particular paging area. Often channel information about a given area is given. · · · · · · · · · · · · · · · · · · · · · · · · ··· ···· · · · · · · ··· ··· ·· ·· ·· A message containing a list of Q channels c currently available to the guest pagers in the area, which are channels c0, cl, ... cQ-1. Home secondary stations and guest secondary stations can share the same channel. For a secondary station whose address code is Y, the channel from the list will be selected as cj, where j = Y MOD Q.

By way of illustration, the following table shows examples for up to 6 channels in the paging region (Q = 1, 2, ... 6).

1 1 Address | Y code 1 j = Y MOD Q Q = 1 1 Q = 2 | 1 Q = 3 1 | Q = 4 AND Q = 5 1 Q = 6 | 1 o 0 1 o 1 AND 0 1 1 o | 0 θ 1 | and 0 1 i | AND 1 1 1 i 1 1 i | 1 2 0 1 θ 1 AND 2 1 1 2 2 2 I 13 0 1 i | 1 0 1 1 ³ I 3 ³ 1 1 ⁴ 0 1 o 1 AND 1 1 1 ° AND 4 4 | 1 5 0 1 i | AND 2 1 | and AND 0 5 1 1 6 0 1 ⁰ 1 I 0 1 1 2 AND 1 θ 1 1 7 0 1 1 1 1 1 ³ 2 i |

· · · · · · · · · · · · · · · · · · · · · · · · · · ·

··· ··· ·· ·· 1 1 _1_1_1_1_1_1 8 and 1 θ | 0 2 0 3 2 9 1 1 ° AND 1 0 1 4 3 10 1 1 θ AND 0 1 2 0 4 11 1 1 θ AND 1 2 3 1 5 12 1 1 o AND 0 0 0 2 0 13 1 1 ° AND 1 1 1 3 1 14 1 1 θ AND 0 2 2 4 2 15 Dec 1 1 o AND 1 0 3 0 3 l etc. 1 | etc. _ etc. _ etc. _ etc. _ etc. _ etc _

Tab. 1: Channel index numbers calculated from the address code

Referring to this table, it is clear that if an available channel report in which the number of channels Q is changed is transmitted, all secondary stations will recalculate their channel numbers j and some secondary stations will have to retune to another channel.

In a simple example, where an operator transmits in every 1, 1000, two channels, the secondary station may be instructed to look at its least significant bit and if it is 99 · <99 9999 • · 999 · 99 9 • 9 9 9 9 ·· · 999 9 9999 999 9 • 9 9 9 9 · φ this zero, tunes the first of two carfals and, if the one is tuned to one, tunes the other of the two channels.

The available channel report will be used by the network to transmit information to the secondary station about adjacent paging areas. The secondary station may use this information for the channel search algorithm.

When the secondary station is in transit when it enters an area, it searches for channels and searches for a channel of acceptable quality. It checks the BZM whether the operator identity and the area code correspond to the operator identity and the area code stored in the memory location 48 (FIG. 1). If a match is found, the secondary station is powered to receive the available channel message and, depending on the parameters in that message, the secondary station selects the appropriate channel and follows a battery saving protocol that the operator disseminates as standard.

Depending on the design of the network and the level of transition services that the operator wants to offer to users, it may not be necessary for it to have its cycle synchronized with the corresponding broadcast on other channels. It is also possible for the transmissions on different channels to be synchronized together for operation in phase offset mode. For flexibility, the secondary station should be able to operate in non-phased and phase-off networks.

In both cases, the multi-channel secondary station must be able to search for other channels if the signal quality of the channel on which it is currently communicating deteriorates. One possible method for determining the quality of the signal is to measure the frequency of bit errors, e.g., code word signals, and if it exceeds a certain threshold, a new channel is searched.

Ftftftftft are not phase synchronized, multichannel secondary station can network or paging areas, and always with that channel in each network or overlap, it is suitable for the transition between ftftftft · ft ·· · · · · · · · · Ftftftft which or

In single-channel networks, switch between synchronizers that hit. This mode of operation by networks or paging areas that do not provide continuous coverage or in situations where the time the secondary station searches the frequencies must be short to avoid missed calls, and in those situations where there is no doubt in which area it has secondary stations work.

Giant. 7 and 8 show an example of phase offset network and phasing of three frequencies in adjacent areas. The phase offset network consists of four AR1 regions. AR2, AR3 and AR4. Primary station PAR1 in area AR1 transmits on frequency F1 in phase T and cycle phasing is shown in the upper line in Fig. 8. Primary station PAR2 in area AR2 transmits on frequency F2 with phase T +, which means shift by one dose period with respect to phase T as shown in the second line of FIG. 8. Primary stations PAR3 and PAR4 in non-overlapping regions AR3 and AR4 transmit at a frequency F3 with a T ++ phase that is shifted by two dose periods relative to the T phase as seen from the lower lines in Fig. 8.

Phasing results in a smooth channel transition, allowing the multi-channel secondary station to locate and sync to a new channel before leaving the previous channel. In this case, the secondary station may switch between the AR1 and AR4 regions and remain connected. To switch between different networks, it is advisable to relate the phase to the absolute normal of time, eg using GPS.

• · · · ············

Three phases in Fig. 9.

In order to have sufficient information on Pw 9 to plan even larger networks than the scan of signal frequencies is not the only one to receive a channel phase in a paging area at a passing secondary station, an appropriate value is assigned in the available channel report as described in the description of FIG. 6.

When the secondary station is in the middle of the operating area, it only receives signals from the local primary station and cannot receive signals from neighboring areas. In this case, the pager may use two more batches, such as the B0 and B2 batches, to monitor signals at other frequencies received from other regions.

The secondary station is not limited to monitoring the two alternating frequencies, see, for example, Fig. 10. While the secondary station is in the center of the AR5 region, it will only receive the F1 frequency but can search the frequencies F2, F3, F4 as shown in Fig. the secondary station moves to the west (Fig. 10), so it can start to receive the frequency F4. When it receives F4. it may stop testing other frequencies in the same phase, eg frequency F3.

So, when the secondary station is searching for active frequencies with a certain phase, it can work with any number of frequencies. When the secondary station has found active frequencies that can transfer its calls, it must monitor only three frequencies.

Obviously, the example of Fig. 11, alternative F2 and F4 in order to search for active possible schemes. In FIG. 11, the secondary station only tests one frequency per dose period. The secondary station may search for active signals at other frequencies at any time when it does not receive its assigned dose on interference.

secondary programmed by the active channel. In this way, many frequencies can be searched. A secondary station can monitor three frequencies in three phase structures only when activity is found at three valid frequencies.

When the secondary station is allowed to select a channel from the available channel report (Fig. 6), it can itself adapt to the network configuration change, which has the following advantages;

a. The secondary stations are distributed approximately equally on the available channels. This optimizes channel load and thus service level.

b. Area frequencies may change, for example, to avoid (Note: this option is only available for stations in the home area that have the frequency of the home area. However, it is possible in the home area if dynamic channel selection is used. ).

c. New frequencies may be added to the paging area to accommodate increasing traffic. If desired, the paging channels may be allocated to the most frequented paging areas to handle large traffic (dynamic channel allocation). In both cases, the secondary station calculates new channels from the available channel report.

d. New paging areas may be introduced. Existing secondary stations in use will use these new areas without having to program the information about the channels being used. In operation, the secondary stations receive the available channel report, decode it and store the data. When the secondary station visits this area next time, it is able to select the appropriate channel without first having to receive a report on the available channels.

Other modifications will be apparent to those skilled in the art upon reading the invention. These modifications may include other features already known from the design, manufacture and use of telecommunications systems and devices and components thereof that may be used in addition to or in place of the features already described herein. Although the claims for certain combinations of properties have been formulated in this patent application, it is understood that the scope of the invention also encompasses any new feature or described either explicitly or by generalization whether or not they relate to the present invention as claimed in any claim whether or not it solves some or all of the same technical problems as the present invention. Applicants hereby acknowledge that the new claims may be formulated to those properties and / or combinations of these properties during the proceedings of this patent application, or any patent application derived therefrom.

a combination of properties here implicitly, or theirs

Usability in industry

Wide range of digital paging systems and other types of cellular communication systems.

Claims (10)

A telecommunications system comprising a plurality of geographically remote primary stations, wherein each primary wherein said primary at least one mobile station defines a coverage area, a network operating station, and a secondary station characterized in that each primary station is adapted to transmit reports of available channels containing information about available radio channels in the network to which they belong, and in that the secondary station has means for receiving available channel messages and selecting one of the channels contained in said message. The system as claimed in claim 1, characterized in that the secondary station has means which, in response to receiving the available channel report, dynamically determine to which of the radio channels of the network the station is to be retuned. The system as claimed in claim 1, characterized in that the number of channels in the network and / or channel frequencies in the network is dynamically changed, and in that the secondary station has means for sensitively receiving a report of available channels for dynamic determination, to which of several radio channels of the network should the secondary stations retune. 4. A system of 2 or 3 as claimed in the claims characterized in that the message 1, the available channels include details of the operator identity and area code, and in that the secondary station comprises means for storing the programmed, at least one operator identity. A system as claimed in any one of claims 1 to 4, characterized in that the secondary station is programmed with a home operator identity and a home area code, and in that the primary station transmits a dose indicator signal comprising the operator identity and the area code , through which the secondary station retuns to its programmed home channel in response to recognizing its home operator identity and home area code and does not scan other channels. The system as claimed in claim 5, wherein the secondary station is programmed with at least one additional home operator identity and home area code and is pending reception in response to detecting said at least one other home operator identity and home area code. reports on available channels from the carrier before selecting the channel. A system as claimed in any one of claims 1 to 6, wherein the system operates according to a protocol comprising a sequence of cycles, each of the cycles comprising a predetermined number of batches comprising a plurality of frames, each frame comprising a plurality of code words indicating wherein the available channel report further includes the phasing details used in each channel. The system as claimed in claim 7, characterized in that adjacent areas of the same network operate at a different frequency, and in that the dose structure used at each frequency is such that similarly identified doses are shifted by one dose period when the secondary station can perform a smooth transmission between the channel frequencies without losing data. The system as claimed in claim 8, characterized in that the channels in each coverage area are assigned one of the predetermined phases so that no two channels in adjacent overlapping geographical areas have the same phase. signal, means belonging to the network and A secondary station for use in a telecommunications system comprising a plurality of geographically remote primary stations operating on a network, characterized in that each primary station is adapted to transmit a channel availability report including radio channel information available on the network 'secondary stations comprising means for receiving channel details storing means sensitive to receiving a report of available channels for selecting details of at least one of the channels contained in the memory means' and adjusting the secondary station accordingly. JUDr, Ivan KOREČEK Advokptn: a patení.ova office 160 00 Praha 6. Na baslr- sv. Jin 9 P.O. BOX 2/5. 160 ij Prague 6