KR20010043144A - Method and apparatus for determining dialed number digit length in fixed wireless telecommunication networks - Google Patents

Abstract

In fixed wireless networks, such as wireless local loop (WLL) networks, a method for an improved call setup process is described. The method includes detecting when the telephone set is dropped by the caller and taken off-hook, where a simulated dial tone is generated at the telephone set receiver in response. When the caller enters the telephone number of the called party, for example, the sequence of the first three digits is compared to a predetermined list of sequences stored in a look-up table. The length of the telephone number is identified by matching the sequence with the associated length in the lookup table before completing the dialing. The call setup process is initiated by passing the input digit to the switching center for processing immediately after the last digit is entered. In the first embodiment, if no sequence match is found, a "time-out" procedure is executed to determine when the last digit is entered to initiate the call setup. In the second embodiment, the sequence is connected to the switch in another way when no sequence is found. The call setup process of the present invention enables effective use of the radio spectrum by potentially requiring no network connection to the switch during dialing when a match is found, potentially increasing network capacity. Moreover, the method eliminates the need for the caller to press "send" when completing dialing, allowing the user to experience calls that more closely resemble traditional wired services.

Description

METHOD AND APPARATUS FOR DETERMINING DIALED NUMBER DIGIT LENGTH IN FIXED WIRELESS TELECOMMUNICATION NETWORKS}

An increasingly popular type of wireless telecommunications network is what is known as a fixed radio network, more generally a wireless local loop (WLL). An important motivation for the adoption of WLL is that it is relatively simpler and more cost-effective to install than traditional wired networks. The relatively high cost of installing a wired network, also referred to as a public switched telephone network (PSTN), is typically associated with the installation of transmission lines and associated equipment. This is particularly the case in rural and other sparsely populated areas, where the cost of installing relatively few lines over long distances can be very high. Therefore, when considering the cost of setting up a new telecommunications network, many operators choose a fixed radio-based solution, such as a WLL, which provides subscribers with excellent access to telecommunications services when connected to a PSTN.

Using radio transmission services instead of wired services significantly saves infrastructure costs, so WLLs are typically acceptable in many areas where setup and installation costs are a major concern. This includes applications that want to quickly and cheaply expand existing telecommunications capacity. Another possible application is for use where local or internal communication is required. These internal communications can be carried through a private branch exchange (PBX) that delivers calls to the correct cohort within a localized environment. Communication with external entities is achieved by linking the PBX to the PSTN. This kind of telecommunication infrastructure is desirable at remote sites configured for short-term (and long-term) use operations, such as oil production sites and remote research locations, for example.

WLL networks and standard wireless mobile telecommunication networks operate in a number of functionally similar ways. For example, a radio path is used when communication between a transceiver unit and a base station (BS) providing a service instead of a wire is operated. The telephone set is connected to a transceiver unit in wireless communication with a BS. As a result, many WLLs are based on Code Division Multiple Access (CDMA) technology, in addition to time division multiple access (TDMA), such as Digital Advanced Mobile Phone System (D-AMPS) and Global System for Mobile Communication (GSM). Operates in accordance with existing standards based on technology. Therefore, they share many of the advantages, such as relatively low installation costs and access to unrestricted telecommunication services, and inconveniences, such as the relatively long call setup time typically associated with existing radio based communications.

As will be appreciated by those skilled in the art, the technique of placing a call into a radio based network is quite different from that of placing a call into a traditional PSTN network. In particular, the WLL call setup process is quite different from the call setup process in a traditional PSTN, whereby the call experienced by the user varies considerably. One notable difference in WLL call setup is the noticeable delay from the time the user dials the dial number when the connection is finally made. This delay can be avoided in radio-based communication systems such as cellular networks, because the link to the switching center (or switch) is generally not instantaneously when the user dials so that the radio spectrum is not fixed during dialing. It is typical.

In a typical call setup process of a radio based network, the caller enters a series of digits representing the desired group's telephone numbers, which are stored as digital data in the telephone set. The digit is then sent to the switching center for processing when the caller presses the 'send' key. This allows the scarce resources of the radio spectrum to be used in an effective manner. When the proper check is completed, if it is determined that a connection can be made, the voice channel is assigned to the call. This process can take several seconds, increasing the delay that the caller detects. This is in contrast to the call setup process in traditional wired systems where the phone is lifted and connected directly to the switch.

In the prior art, much effort has been made to improve the call setup process. One approach is to monitor the elapsed time between dial numbers in an attempt to determine when the user enters the last digit so that the number can be automatically passed to the switch for processing. This method is called a "time-out" method and works by determining that the dial rotation ends when a preset time has elapsed. However, the inconvenience of this technique is that elapsed time imposes additional delay during call setup. A detailed discussion of this technique and other techniques covering call setups can be found in PCT International Publication No. WO 96/32824: A Radio Unit And A Method For Connecting A Fixed Subscriber Station to a WLL System, published October 17, 1996.

In view of the foregoing, it is an object of the present invention to provide a method of eliminating the caller's action of pressing 'send' at the end of a dial so that no immediate connection to the switch is made while the dial is turned. This allows for more effective use of the radio spectrum during the caller setup process, thereby conserving bandwidth. Another object is to reduce the delay in the call setup process compared to the prior art method which uses the "timeout" process to determine the dial digit length to experience a more consistent call in a fixed wireless environment compared to traditional wired.

<Summary of invention>

Briefly, according to this embodiment, the present invention provides a method for determining the length of a telephone number before dialing is completed by the caller to complete the call setup process automatically and before being connected to the switch. Explain. The described method involves, for example, lifting the receiver to detect when the caller takes a standard telephone set off-hook. In response to the off-hook condition, a simulated dial tone is generated by a transceiver station connected to the telephone receiver, and detected by the user to hear the dial tone. The caller enters a series of digits representing the telephone number of the desired group, where a sequence of, for example, the first three input digits is stored in a look-up table in the memory of the transceiver station connected to the telephone set. Is compared to the sequence list. The digit length of the telephone number is identified by restoring the digit length associated with the matching sequence also stored in memory before the caller completes dialing. The call setup process is initiated by passing the input digits to the switching center for processing immediately after the last digit is entered. If the sequence cannot be identified at the compare step, then in the first embodiment a "time-out" procedure is executed to determine when the last digit has been entered to initiate the call setup. In the second embodiment, the connection to the switch is made in a process similar to traditional wired technology to complete the call.

The present invention provides a technique for improving the call setup process in a fixed wireless environment, for example in a wireless local loop, so as to experience in making a call comparable to making a traditional wired call. Moreover, no bandwidth is used during the dialing, which allows for more effective use of the radio spectrum. In another aspect, the present invention also eliminates the need for the caller to press 'send' after entering the telephone number, and in some cases eliminates the delay associated with the "timeout" process when a sequence match is found. These and other advantages of the present invention will become apparent from the following detailed description taken in conjunction with the various drawings.

FIELD OF THE INVENTION The present invention generally relates to radio based wireless telecommunication networks, such as a Wireless Local Loop. In particular, the present invention relates to a technique for determining the digit length before ending the dialing to automatically initialize the call setup.

1 illustrates a simplified wireless local loop (WLL) network.

2A is a flow diagram illustrating a call setup process operating in accordance with a first embodiment of the present invention.

2B is a flow chart illustrating a call setup process operating in accordance with a second embodiment of the present invention.

3 shows an example of a look-up table that can be used in the embodiment.

1 illustrates a simplified radio based wireless local loop (WLL) network. The WLL has a telephone set 100 that is operated using a standard Dual Tone Multiplexed Frequency (DTMF) dial tone coupled to the transceiver station 102. Telephone set 100 is typically a standard telephone set used with traditional landline telephone services to improve the cost effectiveness of the network. Simulated dial tones are generated by the transceiver station 102 at the telephone receiver 100 when the user picks up the telephone. The simulated dial tone is given to the caller as an aid so that the telephone set 100 is very similar to the operation of a traditional landline telephone. The transceiver station 102 may include two-way radio communication via an air interface 103 with an approximately located base station (BS) 104, including all necessary logic. Mobile switching center (MSC) 106 is then connected to BS 104 by digital communication link 108. It should be noted that a typical WLL network includes multiple BSs and the single BS arrangement shown is for illustration. Moreover, multiple telephone sets can be connected to the transceiver station 102 but are not shown for the same reasons.

The WLL network can be operated according to established standards, for example, the Digital Advanced Mobile Phone System (D-AMPS). To complete the call to the external telephone set 112, the MSC 108 is shown connected to the public switched telephone network 114. As in a company, a private branch exchange (PBX) can be used in place of a MSC to connect within a localized environment. Operation of the radio communication over the air interface 103 includes the transmission of at least one control channel and multiple voice channels. The control channel contains commands and control signals necessary for communication between the BS and the transceiver station 102, while the voice channel primarily contains data related to voice communication. In the air interface, the voice channel and the control channel can operate in digital mode, analog mode, or both modes according to the established network protocol. Moreover, when operating in digital mode, the data related to the conversation is transmitted within a time slot designated within the radio frequency carrier, while in analog mode the data is transmitted within a dedicated frequency carrier.

According to the inventive concept, a method for improving the call setup process in a WLL network is described. The method includes a technique for determining the length of a dial number by recognizing an initial sequence of numbers entered before dialing is complete. Since the connection to the switch is not established while the dial is dialed, it can free up part of the radio spectrum to increase the capacity of the network. Moreover, once dialing is complete, the step of requiring the caller to press the 'send' key is eliminated, which in some cases can have the effect of reducing the delay incurred during the call setup process.

Referring now to FIG. 2A, a flow diagram illustrating a method of operation for call setup of a first embodiment operating in accordance with the present invention is shown. In step 200, the telephone set (100 in FIG. 1) is off-hook by the caller who wishes to initiate the call. The off-hook condition is detected by the transceiver station 102, and in step 202 a simulated dial tone is generated and communicated to the telephone receiver to inform the user that everything is operating properly and the telephone is ready for dialing. In step 204, the caller enters the digits of the called party, which are stored in memory in the transceiver station 102 for later transmission to the switch for processing. When the caller enters a digit sequence, step 206 compares the sequence with the corresponding digit length contained in the look-up table of the transceiver station memory. If the sequence is known, that is, sequence matching is found in memory, the transceiver station waits to receive the correct number of digits as specified in the lookup table at step 208. After the correct number of digits has been entered, the transceiver station opens the line to the switch and sends a digit for processing (step 212) to automatically initiate a 'send' process to complete the call. If the sequence is not known (step 210), that is, if the sequence is not found in memory, then a "time-out" operation is performed to determine when the dial rotation is complete. The " timeout " operation assumes that the last digit has been entered after a preset time period in which no digit has been entered. For example, if the phone does not receive an entry within the elapsed time, a 'send' is generated and a time period of approximately 5 seconds is used.

2B illustrates a call setup procedure operating in accordance with a second embodiment of the present invention. The call setup processing step of the second embodiment is substantially the same as the first embodiment up to the point of the comparison step 206. As before, when sequence matching is found, the transceiver station 102 waits to receive the correct number of digits as found in the lookup table of the memory before initiating the call setup shown in step 212 ( Step 208). If no sequence is found, then a connection to the switch is established at step 214, where the call is completed in a conventional manner as in a traditional wired system. When the connection is set up, the transceiver station 102 delivers the received digits and subsequently delivers the user-entered receive digits. This implementation reduces latency compared to using a "timeout" technique, but uses bandwidth to potentially lower the capacity of the network. In some applications where dose is not of primary concern, this may be acceptable or somewhat preferred.

3 illustrates a lookup table that may be used in step 206 in accordance with the present invention. The lookup table includes a series of predetermined sequences stored with the corresponding digit lengths.

According to a preferred embodiment, a series of three digits is typically sufficient to identify the proper length of the called number. Note that more complex numbering structures may require longer sequences to identify lengths. In some countries, various numbering schemes are in place. As an example, in some areas where a special length is usually associated with a prefix or sequence of three digits, a telephone number of a different length is specified. In Sweden, for example, telephone numbers are usually specified six or seven digits long in certain areas of the country or in specific locations within a city. A telephone number with six digits is known and can be easily identified by the prefix of three digits, as indicated by reference numeral 302. Similarly, a telephone number with seven digits can also be identified via prefix 304. Information related to the prefix can be easily obtained through the local telephone company or telecom provider, and this information can be used to update the table entry when the numbering system is modified. Moreover, in countries using a standardized length telephone number system, such as the United States, where virtually all numbers are standard seven digits in length, some special sequences listed in the table, such as 911 emergency calls and attendant assistant calls, for example. The method can be adopted to take advantage of this situation by assuming all seven digit numbers except for.

When dialing long or international numbers, certain prefixes are usually required to be entered on the telephone company's switch to indicate a long distance call. In the United States, callers are typically required to dial 0 (or 1 for direct dialing) + 3 area codes + 7 digits to complete the call. Similarly, international calls are identified by digit 011 (009 in Sweden) + country code + city code + phone number. In localized environments, such as those operating within a PBX, internal telephone numbers or exchanges are typically four or five digits long. The lookup table can be configured to assume a standard length for the exchange in this environment. To dial out of the PBX environment, the caller typically dials 9 or some other number designated for access outside, followed by the telephone number. The lookup table may also be configured to identify if an external line was required and to determine the number of digits to follow by analyzing the next prefix 308 accordingly.

According to an embodiment, the table may be contained in the memory of the transceiver equipment and updated to add / remove or modify entries. In a network operating in accordance with D-AMPS IS-136, the data in the telephone set is updated via radio means, thereby eliminating the need to manually update each telephone. These features are included in Over-the-Air-Teleservice (OATS) functionality, such as Short Message Service (SMS). The transceiver station 102 may be configured to update the lookup table (FIG. 3) using SMS functionality already known, such as multipoint broadcast technology. In this implementation, as is known to those skilled in the art, an SMS message may be displayed to indicate that a particular message includes information about the lookup table. This allows for convenient bulk updates without having to program each station. Note that similar broadcast techniques are used in other standards, such as GSM, and can be used in a similar manner.

The present invention contemplates how the user determines the number of digits dialed before completing the dialing. This allows the system to automatically initiate the call setup process once the last digit is entered, thereby eliminating additional user interference. In the previously discussed embodiment, no connection with the switch is required, so it does not require the use of the radio spectrum while dialing. Moreover, with connections to the switch, the delay associated with call setup experienced in most radio-based telecommunications is sometimes reduced, resulting in a more consistent call compared to traditional wired services.

It is to be understood that the embodiments shown herein are exemplary and that those skilled in the art can change and modify processing steps without departing from the spirit and scope of the invention.

In particular, the present invention is applicable to mobile telecommunication systems, such as cellular systems, in addition to fixed wireless systems. Moreover, mobile terminals can be substituted for the telephone sets and transceivers described in the present invention for fixed wireless applications. Further, the present invention is applicable not only in a single wire terminal environment but also to a multi wire terminal as in a PBX environment. All such changes and modifications are intended to be included within the scope of the present invention as defined by the appended claims.

Claims (15)

A method of initiating a call setup process in a fixed wireless network comprising a switching center, a base station, a transceiver station, and one or more telephone sets, Detecting a condition where a caller enters the telephone set and becomes off-hook; Generating a simulated dial tone audible at the telephone set receiver in response to the detected off-hook condition; Receiving a series of digits from the telephone set, the telephone number of the side inputted and called by the caller; Comparing the input sequence of digits with a preset sequence list and associated digit length stored in a look-up table; Identifying the digit length of the entered number before completing dialing based on the digit length associated with the sequence matching found in the comparing step; And As determined by the digit length, upon receipt of the last digit entered, the call setup is initiated by passing the input digit to the switching center for processing and initializing the call setup when no match is found. "Time-out" is executed to determine the completion of dialing to complete the connection to Method comprising a. The method of claim 1, Said network operating according to a Digital Advanced Mobile Phone System (D-AMPS) standard. The method of claim 1, And the input digit comprises a Dual Tone Multiplexed Frequency tone. The method of claim 1, Said comparing step taking place in said telephone set. The method of claim 4, wherein The preset sequence list is stored in a memory of the telephone set. The method of claim 1, And said preset list is updated by a Short Message Service function. The method of claim 1, Processing by the switching center comprises completing a connection to the called party. The method of claim 1, The switching center operating as a private branch exchange. The method of claim 1, In the initializing the call setup, if the match is not found, the "timeout" process is replaced by establishing a connection to a switch to complete the call. Standard telephone sets; A transceiver station connected to the telephone set; One or more base stations in two-way wireless communication with the transceiver station; A switching center coupled to the one or more base stations; Means for detecting when the telephone set is off-hook; Means for determining when the last digit of the telephone number is entered by the caller by comparing the sequence of telephone numbers with a preset storage list representing the length; And Means for forwarding the entered telephone number to the switching center for processing Fixed wireless network comprising a. The method of claim 10, And said input telephone number is stored in a memory in said telephone set. The method of claim 10, And the sequence is the first three digits of the entered telephone number. The method of claim 10, The preset list is stored in a memory of the transceiver station as a lookup table. The method of claim 10, And said processing of said telephone number comprises means for completing a connection to a called party. The method of claim 10, And said switching center is a branch exchange.