Mobile communications system and method for providing common channel coverage using beamforming antennas

ES 2 531 970 T3

DESCRIPTION

Mobile phone communication system and method of providing common channel coverage using beamforming antennas

Field of the invention

The present invention relates to mobile telephone communication systems. More particularly, the present invention relates to wireless communication systems that support mobile phone unit communications and to a method of increasing capacity through the use of "smart" antennae or beamforming base stations.

Background of the invention

Wireless communication systems are well known in the industry. Generally, such systems comprise communication stations that transmit and receive wireless communication signals between them. Typically, base stations are provided that are capable of conducting simultaneous wireless communications with a plurality of subscriber stations known generically as Wireless Transmit / Receive Units (WRTUs), including mobile phone units. Generally, the term "base station" includes but is not limited to a base station, Node-B, site controller, access point, or other interface device in a wireless environment. The term WTRU includes but is not limited to user equipment, mobile phone station, fixed or mobile phone subscriber unit, pager, or any other type of device capable of operating in a wireless environment.

In Universal Mobile Telecommunications Systems as specified by the 3GPP Third Generation Partnership Project, the base stations are called Node Bs, the subscriber stations are called User Equipments (UEs) and the CDMA interface (Code Division Multiple Access, In English) wireless between Node Bs and UEs is known as Uu interface.

A typical UMTS system architecture in accordance with current 3GPP specifications is depicted in Figure 1a. The UMTS network architecture includes a Core Network (CN) interconnected with a UMTS Terrestrial Radio Access Network (UTRAN) through an interface known as lu which is defined in detail in the current publicly available 3GPP specification documents.

The UTRAN is configured to provide wireless telecommunication services to users through the UEs via the radio interface Uu. The UTRAN has base stations, Node Bs, that collectively provide the geographic coverage for wireless communications with the UEs. In UTRAN, groups of one or more Node Bs are connected to a Radio Network Controller (RNC) through an interface known as a lub in 3GPP. The UTRAN can have several groups of Node Bs connected to different RNCs. RNCs are shown in the example depicted in Figure 1a. In the case where more than one RNC is provided in a UTRAN, communication between RNCs is effected by means of a lur interface.

In existing systems, when a mobile phone unit is turned on for the first time or traverses a coverage region of multiple base stations, a determination must be made as to which base station the mobile phone unit will pair with to carry out wireless communication. Depending on the design of the system, the mobile phone unit, the communication network or the base stations will determine the pairing between each mobile phone unit and a base station.

In one type of communication, a mobile phone unit monitors common signals from all the base stations it receives and synchronizes to the base station with the best quality of service (QoS) signal. In such systems, a beacon signal radiated by each base station is an omni-directional high-power transmission that has a tendency to generate interference.

Smart antennas that include beamforming capability are widely regarded as a promising technology for improving the capacity and / or coverage of wireless radio access systems, such as 3GPP mobile phone communication systems. The distinctive feature of a wireless radio access system employing smart antennas is that a user can be spatially isolated. Radio transmissions directed to or received from a user are isolated in such a way that interference to and from other users is minimized. Figure 1b illustrates a Node B smart antenna focused on a UE of a 3GPP system.

Wireless radio access systems, such as UMTSs that employ smart antennas, infuse double benefits at the system level using highly focused directional antennas. First of all, the

ES 2 531 970 T3 system capacity improves as a result of the reduction in interference generated. Second, system coverage improves, resulting in better link performance. The increase in radio coverage from the use of smart antenna technology represents a particularly attractive feature for wireless communication systems. The application of smart antenna technology, including beamforming, is fairly straightforward once a radio link has been established between a mobile and a radio access point to exchange information on a dedicated channel.

In addition to dedicated radio links, common channels are typically employed in wireless radio access systems. Common channels are established for various purposes, such as: 1) allowing mobile synchronization in time and frequency, for example, a 3GPP Shared Synchronization Channel (SCH Syncronization CHannel); 2) broadcast system information that is essential for registration in the network when power-up occurs, for example on a broadcast channel (BCH - Broadcast Channel, in English) of the 3GPP; and 3) locating mobile phones in idle mode, for example in a paging indicator channel (PICH Paging Indicator CHannel), a paging channel (PCH - Paging CHannel, in English) and a transmission access channel ( FACH - Forward Access Channel, in English) of the 3GPP.

In a statistical sense, the geographic coverage that is provided by the common downlink channels defines the coverage area of ​​a base station, which in UMTS is commonly called a cell. More specifically, the service area provided by a wireless radio access system is determined from the coverage of the common channels.

A significant increase in the cell area covered by a wireless radio access system using smart antenna technology is achieved by employing highly directional antennas that boost the gain of such systems. A gain of a directional antenna can be achieved when the position of an antenna can be estimated by its partner antenna and vice versa. Such circumstances are generally met when a dedicated radio link is established between a mobile and a radio access point.

The use of smart antennas for the transmission and reception of common channels is not defined in the existing 3GPP specifications for wireless radio access systems and the benefits resulting from the use of smart antenna technology have not yet been exploited for transmission. and the reception of common channels. One reason for this is that coverage of common channels such as BCH and PICH must be guaranteed for all mobiles, including those for which the location is unknown. More specifically, a radio access network must ensure that all mobiles can reliably synchronize with the network, read broadcast information, and monitor pages, to name a few. This complication results in wireless radio access systems transmitting common channels using conventional omni-directional antennas that cover entire cells or cell sectors.

In order to match the extended coverage of the dedicated channels using smart antennas, the transmit power of the common downlink channels can be increased. However, an increase in the transmission power by all radio access points, eg base stations, also results in an increase in interference. Such a solution is ineffective in wireless radio access systems that are limited by interference. The present preferred solution takes advantage of smart antenna technology to extend coverage while minimizing interference.

In GB 2 317 786 A a base station directs its beamforming antenna towards a WRTU on the basis of an access request detected at the RACH.

Compendium

The invention is defined by the independent claims.

The present invention makes use of smart antenna technology including beamforming for a wireless radio access system. The functionality of smart antennas for radio links is preferably applied to common channels, which results in a significant increase in cell coverage. An omnidirectional polling pulse is used in connection with the initiation of wireless communications from the mobile phone unit. The polling pulse, a radio frequency (RF) signal with or without intelligence, should not be confused with conventional mobile phone unit uplink channels.

In one embodiment a radio network is provided having a plurality of base stations, each providing wireless communication services in a respective geographic coverage area that may or may not overlap with the geographic coverage areas of another of the base stations. . An interface is connected to the base stations.

Wireless communication is established by first transmitting an omnidirectional polling pulse from a wireless mobile phone unit located in a geographic coverage area of ​​at least one of the base stations. Information regarding the detected poll pulse is communicated to the interface by each base station detecting the poll pulse. One of the base stations that detected the

ES 2 531 970 T3 polling pulse is selected for the communication of the mobile phone unit on the basis of the communication information. The selected base station directs a communication beam to the mobile phone unit to establish wireless communication.

In a non-limiting example of the first embodiment, the radio network is a UMTS Terrestrial Radio Access Network (UTRAN), each base station is a Node B, the interface is a Radio Network Controller (RNC), and the mobile telephone unit is a mobile User Equipment (UE). In such a case, the communication of the corresponding poll pulse information is between the Node Bs and the RNC through an Iub or a combination of Iub / Iur interface through another RNC. The base station selection is preferably performed by the RNC selecting a Node B and the communication established between the selected Node B and the UE is through a Uu interface.

Preferably, each base station has a selectively operable beamforming antenna. Establishing a wireless communication then includes determining a corresponding location of the mobile phone unit relative to the beamforming antenna of the selected base station based on the information regarding the detected polling pulse. Accordingly, directing a communication beam the antenna of the selected base station is operated to form a communication beam that covers a selected portion of the coverage area served by the selected base station that encompasses the corresponding location of the unit. mobile phone.

The communication beam formed preferably contains common channels. In such a case, the antenna of the selected base station is operated to form a communication beam spanning the corresponding location of the mobile phone unit so that other mobile phone units with which the selected base station is conducting a communication. Wireless communication are also encompassed within the formed communication beam such that the formed beam provides common channel service to a plurality of mobile phone units.

If the mobile phone unit does not receive a communication beam directed from a base station within a predefined period of time from its transmission of an omnidirectional polling pulse, the initiation of the communication is preferably restarted. Accordingly, the mobile phone unit is configured to transmit an omnidirectional polling pulse to initiate communication with a base station and to transmit a subsequent polling pulse that may be of higher power if a search beam has not been established. communication from a base station that detected a poll pulse.

Also, the mobile telephony units are preferably configured to monitor the power level of a communication with a base station and to repeat the initiation of the communication if the monitored power level falls below a predefined level. Additionally, the mobile phone units may be configured to transmit a series of higher power omni-directional polling pulses to initiate communication with a base station.

An omnidirectional polling pulse can be transmitted from each of a plurality of mobile phone units. In such a case, information regarding each distinguishable poll pulse from each respective mobile phone unit detected by a base station is communicated to a respective selection interface. Each respective interface selects a base station for each respective mobile phone unit communication on the basis of information regarding the detected polling pulse distinguishable from the respective mobile phone unit of each base station that detected a polling pulse. distinguishable from the respective mobile phone unit. For each respective mobile phone unit for which at least one base station received a distinguishable poll pulse, a communication beam from the respective selected base station is directed towards the mobile phone unit to establish wireless communication.

Preferably, the communication beams formed contain common channels. In some cases, a first base station is selected for communication with a first mobile telephone unit and is also selected for communication with a second mobile telephone unit. The antenna of the first base station is then operated to form a communication beam that spans the relative location of both the first and second mobile telephony units so that the formed beam provides common channel service for the mobile telephony units. both first and second. In other cases a first base station is selected for communication with a first mobile phone unit over a selected first interface and a second base station is selected for communication with a second mobile phone unit over a second selected interface.

When at least one base station receives the polling pulse, measurements can be made to determine a received power level and an estimate of the angle of arrival at the mobile phone unit. This information from one or more base stations can be used to determine the relative location of the mobile phone unit and to direct a communication beam towards the mobile phone unit accordingly.

In a second embodiment, the mobile phone unit selects the base station with which it will establish wireless communication. As in the first embodiment, an omnidirectional sounding pulse is transmitted

ES 2 531 970 T3 from the mobile telephone unit located in a geographical coverage area of ​​at least one of the base stations. A communication beam is directed from the base stations that detect the polling pulse towards the mobile phone unit. One of the base stations that detected the polling pulse is then selected on the basis of the communication beams received by the mobile phone unit. A wireless communication is then established between the selected base station and the mobile phone unit.

The implementing radio network may have a control interface connected to the base stations. In such a case, information regarding the detected poll pulse can be communicated to the interface by each base station that detects the poll pulse. One or more of the base stations that detected the polling pulse can then be chosen or they can be chosen on the basis of the communicated information such that only the chosen base stations direct a communication beam to the mobile phone unit. In this way the radio access network can selectively limit the selection made by the mobile telephone unit.

A preferred mobile includes a transmitter configured to transmit an omnidirectional poll pulse and a receiver to receive communication beams from base stations that detected a poll pulse transmitted by the mobile phone unit. To implement the second embodiment, the mobile phone unit includes a processor configured to select a base station with which to establish wireless communication based on the communication beams received by the mobile phone unit from the base stations that detected a polling pulse transmitted by the mobile phone unit.

Each mobile phone unit can be equipped with a Global Positioning System (GPS). In such a case, the mobile telephony units are preferably configured to transmit an omnidirectional polling pulse that includes the location information of the mobile telephony unit determined by its GPS. The mobile telephony units may also be configured to transmit an omnidirectional polling pulse that includes the identification information of the mobile telephony unit.

Other objects and advantages of the present invention will be apparent to those skilled in the art from the following detailed description and corresponding drawings.

Brief description of the drawings

Figure 1a represents a typical UMTS system architecture in accordance with current 3GPP specifications.

Figure 1b illustrates a Node B smart antenna focused on a UE of a 3GPP system.

Figure 1c illustrates a UE moving through cells covered by a Node B base station network of a 3GPP system employing smart antennas.

Figure 2 is a flow chart of a base station selection procedure in accordance with one embodiment of the present invention.

Figure 3 is a flow chart of a variation of a base station selection procedure in accordance with one embodiment of the present invention.

Figure 4 is a flow chart of a reselection procedure in accordance with one embodiment of the present invention.

Detailed description of the preferred embodiments

The present invention is described with reference to the drawing figures in which like numbers represent like elements throughout. The present invention can be applied to some or all of the common downlink channels of the systems. For the sake of simplicity, the invention is described herein as common downlink channels apply to a UMTS system. However, the proposed invention is applicable in any wireless system.

The present invention provides a wireless radio access network having networked base stations with an improved base station selection mechanism for mobile phone units, i.e., mobile phone WTRUs, as they enter and / or or they roam through respective geographic coverage areas provided by the respective base stations. Such mobile phone units, for example the UEs illustrated in Figure 1a, generally include a transmitter, a receiver, and a communication signal processor. The network preferably includes some type of base station interface that makes the selection. Such an interface for the Node Bs of a 3GPP network is a Radio Network Controller (RNC). However, an alternative embodiment provides self-selection by the mobile phone unit.

Rather than providing complete uniform coverage across an entire cell or cell sector, a base station selectively directs at least some, but preferably all, of the common channels of

ES 2 531 970 T3 downlink to individual mobile phone units using smart antenna technology, including beamforming. Figure 1b illustrates such coverage in a 3GPP system by a Node B for a mobile phone unit UE1 roaming in a cell indicated in dotted lines. Preferably, the coverage by a base station of a common downlink channel or beacon channel matches that of dedicated channels using smart antennas.

A pattern of mutually exclusive cells can be mapped to denote the global coverage area of ​​a wireless radio access network as illustrated in dotted lines in Figure 1c. However, the actual geographic coverage area capable of being served by each base station typically extends beyond the nominal cell mapping and overlaps with the actual geographic coverage area of ​​neighboring base stations. For example, in Figure 1c, the mobile phone unit UE is represented as capable of being served by at least some of the base stations BS1, BS2 or BS4.

Figure 2 is a flow chart of a base station selection procedure in accordance with one embodiment of the present invention. In a first step 202, a mobile phone unit emits a polling pulse using a directional antenna to produce a uniformly radiated radio frequency (RF) pattern. Each base station that receives the poll pulse communicates that information to a Radio Network Controller (RNC) as indicated in step 204. For example, a polling pulse emitted by the mobile phone unit UE in Figure 1c would most likely be received by the base stations BS2 and BS4, but could also be received by the base station BS1 and possibly by the base stations BS1. base BS6 and BS7 as well.

The receiving base stations may or may not be controlled by the same RNC. When more than one RNC is involved, preferably the one that first receives a communication from one of its associated Node B base stations becomes the deciding RNC and has the receipt of the probe pulse information conveyed to it by the one (s). RNCs associated with the other base station or the other base stations receiving or receiving the polling pulse such as through a standard Iur interface as illustrated in Figure 1a. When a base station is in another UTRAN, communication to the deciding RNC can be performed through the core network of an existing 3GPP system.

The RAN selects one of the pulse receiving base stations and determines the direction from the selected base station to the mobile phone unit as reflected in step 206. The selection decision is preferably based on the received signal power . When more than one base station receives the polling pulse above a selected minimum power, other standard QoS quality of service criteria can be compared in the selection process. Also, overall network traffic can be considered in the selection decision as described in US Patent Application No. 10 / 305,595 owned by the assignee of the present invention.

When the deciding RNC is not the RNC directly associated with the selected base station, the RNC of the selected base station can be used to determine the direction from the selected base station to the mobile phone unit. However, when evaluating global network traffic the RNC (s) can communicate all data to the core network and the core network can be used to assist in or effect base station selection. Such alternatives can be activated when the communication traffic with respect to an RNC or UTRAN reaches certain specified minimum levels. As implied in Figure 1c, even though the base stations BS2 and BS4 are closer to the mobile phone unit UE, the base station BS1 can possibly be selected on the basis of considerations about QoS and the global network traffic.

As indicated in step 208, once selected, the selected base station directs its transmission on the common downlink channels to the mobile phone unit as shown in Figure 1b. The base station is preferably provided with a beamforming antenna for this purpose and the direction of the beam is preferably based on an estimate of the location of the mobile phone unit. Directional antennas, phase matrix antennas and other types of antenna systems can be provided such that a beam from a base station antenna for transmission and / or reception covers a particular geographic area of ​​a specific shape and size. The location estimate can be inferred in various ways, but is preferably based on information regarding the reception of the polling pulse by one or more base stations. Quantitative measurements of the power and / or beam reception angle of the one or more base stations can be used in a conventional way to calculate the location of a corresponding mobile telephone unit. In a 3GPP type system, this can be done either at the RNC or at Node B. Alternatively, geolocation data may be added to the polling pulse by the mobile phone unit and a relative position determined by comparison with the known location of the selected base station antenna. The mobile phone unit may be equipped with a Global Location System (GPS) for this purpose.

The probe pulse is a physical signal that is preferably transmitted using an isotropic antenna, which is an antenna that radiates or receives equally in all directions. The shape of the polling pulse preferably depends on the radio access technology. For example, in CDMA-based systems, a burst

Very short duration ES 2 531 970 T3 spanning multiple chips, a short sequence of chips can represent the probing pulse.

The timing for the poll pulse depends on the implementation and realization of the physical signal, which is dependent on radio access technology. Each wireless communication medium requires a different pulse timing structure. For example, a FDD-CDMA poll pulse would be different from a TDD-CDMA poll pulse.

The physical signal defining the probing pulse itself can be made with an Aloha or slotted Aloha technique. In an Aloha-type technique, the mobile phone unit simply transmits the polling pulse burst whenever it wishes. There are no timing restrictions in the Aloha type system. If the mobile phone unit does not get a response from a base station, this is considered a "connection" failure. A back-off procedure is then implemented. This procedure essentially performs a connection retry after the mobile phone unit waits a random amount of time for retransmission.

In the slotted Aloha type technique, the mobile phone unit transmits the polling pulse at specific time intervals. This technique requires some kind of master timing. In the event of a failure, the reconnection procedure corresponds to a mobile phone unit waiting for a random number of time slots until the mobile phone unit retransmits.

In some situations, multiple mobile phone units may have pulses at the same time to grab the attention of the same RAN. When this occurs and the Node Bs can differentiate the signals from the two mobile phone units, the RAN selects the Node Bs to direct the common channels to each mobile phone unit. If the Node Bs cannot differentiate the signals from each mobile phone unit, the RAN cannot make a proper Node B selection to direct the common channels to each mobile phone unit. In this case, the selection preferably waits for the next pulse transmitted by each mobile phone unit. To ensure that subsequent pulses from these mobile phone units do not collide, a preferred reconnection procedure for mobile phone units includes waiting a random amount of time before retransmitting a polling pulse, thus avoiding another collision. Successive pulses can be at higher power as explained in the variation that follows.

A variation of the procedure illustrated in Figure 2 is presented in Figure 3. Once the mobile phone unit enters a network service area, step 302, it issues a first polling pulse at a lower power, step 304. However, instead of a single pulse, the mobile phone unit emits a series of pulses and gradually increases the transmit power during the emission of the series of polling pulses, step 306. Preferably, each successive pulse is transmitted with a greater power than its immediate predecessor pulse.

One or more base stations that each detect at least one poll pulse report their poll pulse receive information to a RAN, step 308. The RAN selects one of the base stations and calculates the relative location of the polling unit. mobile phone, step 310. The base station selected below directs one or more common downlink channels to the mobile phone unit using smart antenna technology, step 312. The mobile phone unit then receives the downlink channels and can then begin communications with another unit through the selected base station, step 314.

In any embodiment, when it detects a polling pulse, the Radio Access Network (RAN) preferably uses measurements made on the polling pulse to then direct the transmission of selected base stations from one. or many common downlink channels using a smart antenna. For example, the strength of the signal received from the polling pulse and the angle of arrival of the signal with respect to a single base station can be used to determine the position of the mobile phone unit and the direction in which they should be. common channels radiated using smart antennas. However, the RNC can correlate data received from all base stations that report receipt of the polling pulse to make a more accurate calculation of the geographical location of the mobile phone unit.

A mobile phone unit preferably makes its presence known to the RAN when power-up or when entering a UTRAN service area. Accordingly, the base stations must try to find polling pulses at regular time intervals, or continuously in order to detect the emergence of new mobile phone units. Furthermore, in order to maintain a relationship with a particular base station, the mobile telephony units that are in a particular base station, that is, they are not actively communicating, preferably schedule periodic pulses to ensure the tracking the location of the mobile phone unit so that communications directed to such a mobile phone unit can be quickly connected.

ES 2 531 970 T3

To facilitate the transmission and detection of the poll pulse, certain common downlink channels that provide timing information regarding access opportunities for the uplink poll pulse may be transmitted using omnidirectional antennas. However, this is preferably carried out only if the coverage of such synchronization channels can be ensured without sacrificing downlink capacity.

In a variation of the embodiment of Figure 3, a series of poll pulses are sent according to an increasing power procedure as follows. A mobile phone unit transmits an initial poll pulse at a low power level as in step 304. After a period of time without receiving a response from a base station, the mobile phone unit will increase the transmitted power and try your probing impulse again. The procedure is repeated until sufficient downlink communication is received from a base station. In other words, step 306 is skipped, or stopped, once steps 308, 310, and 312 have been executed. The amount of time until the transmission of a higher power "boost" poll pulse can be set or determined from a random reconnection process carried out by the mobile phone unit. Additionally, the amount of power increase for each stage can also be fixed or variable.

In addition to or as an alternative to transmitting a polling pulse when entering a service area, the mobile phone unit can be configured to transmit a polling pulse when the received signal code strength (RSCP - Received Signal Code Power) of one or more selected common channels falls below a certain threshold level. Also, once the radio access network has determined the location of the mobile phone unit, the registration and authentication information is preferably exchanged between the network and the mobile phone unit. Network registration is preferably done using conventional protocols as in current wireless systems.

Although the invention relates to the use of smart antennas on the downlink and common channels, the uplink registration and authentication information is not required to be transmitted using smart antennas. During other sleep mode operation, including location monitoring, system updates, and broadcast information, network synchronization and other procedures are ensured by a mechanism that uses polling pulses to track displaced mobiles. A displaced mobile is a mobile phone unit that has emerged out of the gloom of the focused antenna of the base station that had been selected for communication with the mobile phone unit.

As in discontinuous reception for conventional UMTS systems, a mobile phone unit in idle mode must "wake up" and obtain one or more channels such as location channels or updates to system information on a broadcast channel (BCH). . If the received power on the desired common or common channel (s) is insufficient, the mobile phone unit may be configured to transmit a polling pulse so that the radio access network can redirect the transmission of common channels using an antenna. smart base station.

Another application is made for mobile telephony units that use a conventional DRX cycle. A DRX cycle is a mode in which a mobile phone unit reverts to when it loses contact with the network. If a mobile phone unit becomes disconnected from the network, the mobile phone unit will preferably periodically transmit a poll pulse every XRD cycle before obtaining common channels according to the invention as described above.

As a mobile phone unit passes through a coverage area and more specifically when it leaves the coverage area of ​​a given cell, there is a need for reselection of an appropriate base station to facilitate communications with the unit. mobile phone. This can be done according to the process described above using a base station interface device such as a 3GPP RNC. Alternatively, a mobile phone unit may be configured to be itself capable of selecting or reselecting a base station.

Although a mobile phone unit self-selection is equally applicable for initiating a wireless communication, a self-selection reselection procedure according to the second embodiment of the present invention is presented in Figure 4. In the case of reselection, the mobile phone unit monitors the received power of a common downlink channel transmitted by a currently selected base station to determine if it falls below a preselected threshold, step 402. When the threshold is exceeded, the mobile phone unit transmits a polling pulse, step 404. When receiving the poll pulse, neighboring base stations receiving the pulse direct the downlink common channel transmission to the mobile phone unit, step 406.

Figure 1c represents the case in which the base station BS1 was previously selected to serve the communications for the mobile telephone unit UE which has issued a poll pulse after leaving the nominal cell served by that base station. The figure illustrates the base stations BS2 and BS4, which have received the impulse, directing the common downlink channels, for example a beacon channel, towards the mobile telephone unit UE. In this alternative embodiment, the mobile phone unit selects a base station

ES 2 531 970 T3 based on a comparison of the reception of the common downlink channels of such neighboring base stations, step 408. Preferably, a cell registration process is then executed by means of the base station just selected to appropriately re-designate the location of the mobile telephony units with respect to the network, step 410.

The radio access network can control which cell a mobile phone unit selects by virtue of its control of base station transmissions. When receiving the poll pulse from multiple base stations, an RNC can estimate the location of the mobile phone unit using triangulation techniques and measurements from all base stations in the poll pulse. The radio network controller may use the location of the mobile phone unit to direct the transmission of common channels from only one base station, ie the one for which the RNC chooses that the mobile phone unit should select. This type of control is particularly useful when evaluating overall network usage and the capacity of particular Node Bs, so that better utilization of network resources is provided at any given time.

Polling pulses can be generated at a frequency outside of normal uplink and downlink telecommunication frequencies, thereby alleviating frequency congestion. For example, in a current CDMA deployment, mobile phone units are typically assigned separate channels at least 1.25 MHz, providing approximately 42 channels under the current frequency assignment scheme. Typically, the uplink transmission frequency is 45 MHz lower than the downlink transmission frequency. The polling pulses are preferably then assigned to a frequency in close proximity to the uplink and downlink, but not on the same frequency as the uplink or downlink transmissions.

Typically the poll pulse is preferably a simple short signal, containing no specific information, but optionally the poll pulse may contain identification information of the mobile phone unit. With such information, base stations can easily determine and distinguish between simultaneously received pulses from more than one mobile phone unit. This information can indicate the reason why the mobile wants to connect to the network. For example, the mobile phone unit may wish to simply register with the network or it may wish to establish a call.

The scope of the protections is defined by the appended claims.