Abstract:
A technique for preventing the user of a wireless terminal from carrying a wireless terminal into the umbra of a fade is disclosed. In particular, some embodiments of the present invention notify the user that the user is in danger of entering the umbra and assist the user in navigating from the fade. An illustrative embodiment of the present invention comprises: creating a first measurement of signal quality, SQ(n), of a signal received from a wireless terminal; and, when the first measurement of signal quality, SQ(n), is unsatisfactory, transmitting a first message to the wireless terminal to direct a user of the wireless terminal to move the wireless terminal in one direction.

Description:
FIELD OF THE INVENTION 
     The present invention relates to telecommunications in general, and, more particularly, to a technique for preventing a wireless telecommunications call from being disconnected due to low signal quality. 
     BACKGROUND OF THE INVENTION 
     FIG. 1 depicts a schematic diagram of a portion of a typical wireless telecommunications system, which provides wireless telecommunications service to a number of wireless terminals (e.g., wireless terminals  101 - 1  through  101 - 3 ) that are situated within a geographic region. The heart of a typical wireless telecommunications system is Wireless Switching Center (“MWSC”)  120 , which may be also known as a Mobile Switching Center (“MSC”) or Mobile Telephone Switching Office (“MTSO”). Typically, Wireless Switching Center  120  is connected to a plurality of base stations (e.g., base stations  103 - 1  through  103 - 5 ) that are dispersed throughout the geographic area serviced by the system and to the local- and long-distance telephone offices (e.g., local-office  130 , local-office  138  and toll-office  140 ). Wireless Switching Center  120  is responsible for, among other things, establishing and maintaining calls between wireless terminals and between a wireless terminal and a wireline terminal, which wireline terminal is connected to Wireless Switching Center  120  via the local and/or long-distance networks. 
     The geographic area serviced by a wireless telecommunications system is divided into spatially distinct areas called “cells.” As depicted in FIG. 1, each cell is schematically represented by a hexagon; in practice, however, each cell has an irregular shape that depends on the topography of the terrain surrounding the cell. Typically, each cell contains a base station, which comprises the radios and antennas that the base station uses to communicate with the wireless terminals in that cell and also comprises the transmission equipment that the base station uses to communicate with Wireless Switching Center  120 . 
     For example, when wireless terminal  101 - 1  desires to communicate with wireless terminal  101 - 2 , wireless terminal  101 - 1  transmits the desired information to base station  103 - 1 , which relays the information to Wireless Switching Center  120 . Upon receipt of the information, and with the knowledge that it is intended for wireless terminal  101 - 2 , Wireless Switching Center  120  then returns the information back to base station  103 - 1 , which relays the information, via radio, to wireless terminal  101 - 2 . 
     When wireless telecommunications system  100  is a terrestrial system, in contrast to a satellite-based system, the quality and availability of service is subject to the idiosyncrasies of the terrain surrounding the system. For example, when the topography of the terrain is hilly or mountainous, or when objects such as buildings or trees are present, a signal transmitted by a base station can be absorbed or reflected such that the signal quality is not uniform throughout the cell. The result is that some areas of the cell might receive little or no signal from the base station because they are in the shadow of a mountain or a building. Alternatively, some areas can receive a direct path signal and one or more reflected signals from the base station such that the signals destructively interfere in accordance with the well-known multipath problem. In either case, for the purposes of this specification, a region of poor signal quality is called a “fade.” 
     FIG. 2 depicts a schematic diagram of cell  102 - 1  of FIG. 1, which contains base station  1031 , wireless terminal  101 - 1 , fade  201 - 1  and fade  201 - 2 . In general, the shape, intensity and area of a fade is based on terrestrial features. 
     At the perimeter or “penumbra” of a fade, the signal quality is typically diminished a little such that a call between the wireless terminal and the base station can continue, although generally with either noise or lapses in the conversation. At the interior or “umbra” of the fade, the signal quality is typically so attenuated that the base station and the wireless terminal cannot communicate at all. 
     When the user of a wireless terminal carries the wireless terminal into the umbra of a fade while engaged in a call, the call is invariably dropped, which annoys the parties to the call and deprives the operator of the wireless telecommunications system of revenue. Therefore, the need exists for a technique for eliminating or ameliorating the effect of a fade, or of preventing the user of a wireless terminal from carrying the wireless terminal into the umbra of a fade while engaged in a call. 
     SUMMARY OF THE INVENTION 
     Some embodiments of the present invention prevent the user of a wireless terminal from carrying a wireless terminal into the umbra of a fade without some of the costs and restrictions associated with techniques in the prior art. In particular, some embodiments of the present invention notify the user that the user is in danger of entering the umbra and assist the user in moving away from the fade. Furthermore, some embodiments of the present invention work with existing wireless terminals and without a change to the telecommunications air interface. This fact is particularly advantageous because it enables some embodiments of the present invention to be commercially exploited without changing the millions of wireless terminals already in existence. 
     Some embodiments of the present invention reside outside of the wireless terminal and estimate when a wireless terminal is in a fade by monitoring at the base station the signal quality of the signal transmitted by the wireless terminal. The is premised on the observation that if the wireless terminal is having difficulty receiving a signal from the base station because it is in a fade, the base station will perceive a similar difficulty in receiving a signal from the wireless terminal. In other words, the signal quality at the wireless terminal is determined not directly by the wireless terminal, but indirectly. 
     When the signal quality of a signal from the wireless terminal becomes unsatisfactory, which indicates that the wireless terminal has entered a fade, the wireless telecommunications system inserts an audible message into the downlink audio channel that is heard by the user of the wireless terminal. Typically, the message: (1) informs the user that the call is in danger of being dropped because the user has carried the wireless terminal into a region of unsatisfactory signal quality, and (2) directs the user to take remedial measures. 
     Because some embodiments of the present invention specify neither the absolute direction of movement nor are capable of explicitly determining the direction of movement, some other embodiments of the present invention continually measure the signal quality from the wireless terminal and provide feedback to the user on whether the user&#39;s remedial movement is satisfactory, or better but not yet satisfactory, or has made the situation worse. In other words, because some embodiments of the present invention know neither the absolute direction of the user&#39;s movement nor the shape of the fade, the illustrative embodiment uses changes in successive signal quality measurements to provide feedback to the user about the efficacy of user&#39;s movements to escape the fade. 
     In other words, some embodiments of the present invention function somewhat analogously, although not identically, to a high-tech version of the children&#39;s game Huckel-Buckel-Beanstalk. In Huckel-Buckel-Beanstalk one child, who knows the location of a hidden object, guides a second child, who does not know the location of the hidden object, to the hidden object by continually providing feedback to the second child as the second child moves in search of the object. Traditionally, the first child&#39;s feedback is manifested with adjectives normally associated with temperature, such as “colder,” “warmer,” and “burning up!” When the second child is stationary and far from the hidden object, the first child might say “frigid.” As the second child moves towards the hidden object, the first child would provide positive feedback by saying “warmer.” If, instead, the second child moves away from the hidden object, the first child would provide negative feedback by saying “colder.” Through successive iterations of movement by the second child and feedback by the first child, the second child is progressively given sufficient information to zero-in on the location of the hidden object. 
     In Huckel-Buckel-Beanstalk, the first child explicitly knows through direct observation the location of the hidden object, the location of the second child, and the second child&#39;s absolute direction of movement. In contrast, some embodiments of the present invention know neither the location of a fade, the location of the wireless terminal, nor the absolute direction of movement of the wireless terminal as it is moved by the user. Furthermore, the goal of Huckel-Buckel-Beanstalk is to assist another person in moving towards an object; in contrast, the goal of some embodiments of the present invention is to assist another person in moving away from a region in space (i.e., a fade). 
     Embodiments of the present invention deduce the distance of the wireless terminal from a fade based on signal quality measurements, and deduce the direction of movement towards or away from a fade based on the changes in successive signal quality measurements. An unsatisfactory signal quality measurement enables an embodiment of the present invention to deduce that a wireless terminal is near a fade and to sound a tocsin. An improvement in successive signal quality measurements enables the embodiment to deduce that the wireless terminal is moving away from the fade and to provide positive feedback to the user, and declining signal quality measurements enable the embodiment to deduce that the wireless terminal is moving toward the fade and to provide negative feedback to the user. 
     An illustrative embodiment of the present invention comprises: creating a first measurement of signal quality, SQ(n), of a signal received from a wireless terminal; and, when the first measurement of signal quality, SQ(n), is unsatisfactory, transmitting a first message to the wireless terminal to direct a user of the wireless terminal to move the wireless terminal in one direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a schematic diagram of a wireless telecommunications system in the prior art. 
     FIG. 2 depicts a schematic diagram of a cell and a plurality of fades within that cell. 
     FIG. 3 depicts a block diagram of an illustrative embodiment of the present invention. 
     FIG. 4 depicts a block diagram of a base station in accordance with the illustrative embodiment of the present invention. 
     FIG. 5 depicts a block diagram of a channel quality processor in accordance with the base station of FIG.  4 . 
     FIG.  6 . Depicts a flowchart that illustrates the operation of the illustrative channel quality processor of FIG.  5 . 
     FIG. 7 depicts a graph of signal quality as a function of measurement cycle for an illustrative signal. 
     FIG. 8 depicts a block diagram of an illustrative wireless terminal in accordance with one embodiment of the present invention. 
     FIG. 9 depicts a block diagram of an illustrative wireless terminal in accordance with a second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 3 depicts a block diagram of an illustrative embodiment of the present invention, which advantageously comprises: wireless switching center  301 , base station  302  and wireless terminal  303 . When wireless terminal  303  is engaged in a call, two independent, half-duplex communications channels are established between wireless terminal  303  and base station  302 , in well-known fashion. One half-duplex channel carries information from base station  302  to wireless terminal  301  and is called the downlink channel or, alternatively, the forward channel. The second half-duplex channel carries information from wireless terminal  301  to base station  302  and is called the uplink channel or, alternatively, the reverse channel. 
     The uplink channel received by base station  302  is forwarded to wireless switching center  301  over link  306 , in well-known fashion, and the downlink channel is received from wireless switching center  301  over link  307 , also in well-known fashion. 
     FIG. 4 depicts a block diagram of base station  302  in accordance with the illustrative embodiment. Base station  302  advantageously comprises: receive antenna  401 , front-end  402 , demodulator  404 , decoder  406 , channel quality processor  410 , encoder  412 , modulator  414 , transmitter  416  and transmit antenna  417 , interconnected as shown. 
     Uplink signal  305  is received by receive antenna  401  and processed by front-end  402 , which prepares uplink signal  305  for demodulation by demodulator  404 , in well-known fashion. Front-end  402  advantageously measures the signal quality of uplink signal  305 , in well-known fashion, and sends the resulting measurement to channel quality processor  410  via lead  408 . Front-end  402  can measure the signal quality of uplink signal  305  according to any of one or more criteria (e.g., signal-to-noise ratio, absolute power in dBm, etc.). It will be clear to those skilled in the art how to make and use receive antenna  401  and front-end  402 . 
     Demodulator  404  advantageously demodulates uplink signal  305 , in well-known fashion, according to the appropriate modulation scheme and provides the demodulated uplink signal to decoder  406 . Decoder  406  advantageously decodes the uplink signal, in well-known fashion, and provides the decoded uplink signal to channel quality processor  410  on lead  407 . Decoder  406  also advantageously determines a measurement of signal quality of uplink signal  305  based on the error rate of the decoded uplink signal and provides that measurement to channel quality processor  410  on lead  409 . For example, when wireless terminal  303  and base station  302  are IS-95A CDMA compliant, the measurement of signal quality from decoder  409  is advantageously based on the frame error rate of the signal. It will be clear to those skilled in the art how to make and use demodulator  404  and decoder  406 . 
     Channel quality processor  410  advantageously receives: (1) the measurement of signal quality on lead  408 , (2) the measurement of signal quality on lead  406 , (3) the decoded uplink signal on lead  407 , and (4) the downlink signal from wireless switching center  310  on lead  307 , and outputs: (1) an occasionally modified downlink signal to encoder  412 , and (2) an occasionally modified uplink signal to wireless switching center  301  on lead  306 . Channel quality processor  410  will be described in detail below. 
     The downlink signal from channel quality processor  410  is successively provided to encoder  412 , modulator  414 , transmitter  416  and transmit antenna  417 , in well-known fashion, for transmission to wireless terminal  303 . 
     FIG. 5 depicts a block diagram of channel quality processor  410 , which advantageously comprises: threshold detector  501 , controller  502 , summer  503  and summer  504 . Threshold detector  501  advantageously receives both: (1) the measurement of signal quality on lead  408 , and (2) the measurement of signal quality on lead  406  and uses one or both measures to create a quantitative measurement of signal quality, SQ(n), of uplink signal  305 . Threshold detector  501  advantageously passes the measurement of signal quality, SQ(n), to controller  502 . It will be clear to those skilled in the art how to make threshold detector  501 . 
     Controller  502  is advantageously an appropriately-programmed general-purpose processor or a hardwired special-purpose processor and the operation of controller  502  is most clearly understood in conjunction with the flowchart depicted in FIG.  6  and the illustrative graph of signal quality in FIG.  7 . 
     At step  601 , controller  502  advantageously resets a counter, n, to zero at the beginning of each call with wireless terminal  303 . 
     At step  602 , controller  502  advantageously increments the counter, n, by one to n= 1 . 
     At step  603 , controller  502  receives a measurement of signal quality, SQ(1), of the uplink signal received from wireless terminal  303 , with the assistance of threshold detector  501 , as described above. 
     FIG. 7 depicts an illustrative graph of the signal quality, SQ(n), of the uplink signal as a function of the counter n. Typically, the signal quality of the uplink signal fluctuates as the user of wireless terminal  303  moves about. 
     At step  604 , controller  502  determines if the current measurement of signal quality, SQ(n), is satisfactory, which suggests that wireless terminal  303  is not in a fade. In accordance with the illustrative embodiment, when a measurement of signal quality, SQ(n), is above the threshold, T 1 , the signal quality is deemed satisfactory and controller  502  estimates that wireless terminal  303  is not in a fade. When the measurement of signal quality, SQ(n), is deemed satisfactory, control passes to step  602 . In contrast, when the measurement of signal quality, SQ(n), is deemed unsatisfactory (i.e., when SQ(n) is less than T 1 ), control passes to step  605 . Because it can be seen from the graph in FIG. 7 that SQ(1) is above a threshold, T 1 , control passes to step  602 . 
     Typically, a value for T 1  is established that is that indicative of the penumbra of a fade—the theory being that if it can be detected that the wireless terminal is in the penumbra before it enters the umbra, the communications channels are still functioning and remedial measures can still be taken. In contrast, if a value for Tj is established that is too low, the wireless terminal will enter the umbra and communications will fail before the opportunity for remedial action is possible. 
     At step  602 , controller  502  advantageously increments the counter, n, by one to n=2. 
     At step  603 , controller  502  receives a measurement of signal quality, SQ(2), of the uplink signal received from wireless terminal  303 , with the assistance of threshold detector  501 , as described above. 
     At step  604 , controller  502  determines if the current measurement of signal quality, SQ(2), is satisfactory. Because it can be seen from the graph in FIG. 7 that SQ(2) is above the threshold, T 1 , control again passes to step  602 . 
     At step  602 , controller  502  advantageously increments the counter, n, by one to n=3. 
     At step  603 , controller  502  receives a measurement of signal quality, SQ(3), of the uplink signal received from wireless terminal  303 , with the assistance of threshold detector  501 , as described above. 
     At step  604 , controller  502  determines if the current measurement of signal quality, SQ(3), is satisfactory. Because it can be seen from the graph in FIG. 7 that SQ(3) is not above the threshold, T 1 , control passes to step  605 , which suggests that wireless terminal  303  has entered a fade. Although the measurement of signal quality, SQ(3), is below T 1 , the fact that it can be measured at all suggests that wireless terminal  303  is in the penumbra of a fade and not totally in the throes of the umbra. 
     At step  605 , controller  502  advantageously generates a first message that: (1) indicates that wireless terminal  303  has entered a fade and that the call is in danger of being dropped, and (2) directs the user of wireless terminal  303  to move a short distance in one direction, preferably the direction from which the user just came. The first message is advantageously a pre-recorded or synthesized audible message that is perceivable and understandable by the user of wireless terminal  303 . Controller  502  then outputs the message to summer  504  where it is advantageously inserted, in well-known fashion, into the downlink audio channel that is being transmitted to wireless terminal  303 . 
     Alternatively, the message is a control message that that: (1) indicates that wireless terminal  303  has entered a fade and that the call is in danger of being dropped, and (2) directs the user of wireless terminal  303  to move a short distance in one direction, preferably the direction from which the user just came. In this case, controller  502  outputs the message to summer  504  wherein summer  504  inserts the control message into the downlink control message stream, in well-known fashion. Clearly, when the message is in the form of an audible message that is inserted into the downlink audio channel, the illustrative embodiment functions with existing wireless terminals and extant telecommunications air interface standards. In contrast, when the message is in the form of a control message that is inserted into the downlink control message stream, a wireless terminal, such as that depicted in FIG. 8 or FIG. 9 must be employed, and the air interface must be amended accordingly. The wireless terminals in FIG.  8  and FIG. 9 will be described in detail below. 
     Simultaneously, controller  502  advantageously generates a second message that indicates that: (1) wireless terminal  303  has entered a fade and that the call is in danger of being dropped, and (2) the user of wireless terminal  303  may be temporarily distracted from the conversation pending action to prevent the call from being dropped. Advantageously, the second message is advantageously a pre-recorded or synthesized audible message that is perceivable and understandable by a human. Controller  502  then outputs the second message to summer  503  where it is advantageously inserted, in well-known fashion, into the uplink audio channel that is being transmitted to wireless switching center  301  on lead  306 . From step  605 , control passes to step  606 . 
     At step  606 , controller  502  advantageously increments the counter, n, by one to n=4. 
     At step  607 , controller  502  receives a measurement of signal quality, SQ(4), of the uplink signal received from wireless terminal  303 , with the assistance of threshold detector  501 , as described above. Advantageously, the measurement of signal quality, SQ(4), is delayed until the user of wireless terminal  303  has received the most recently transmitted message and has had an opportunity to move. 
     At step  608 , controller  502  determines if the current measurement of signal quality, SQ(4), is satisfactory. Because it can be seen from the graph in FIG. 7 that SQ(4) is not above the threshold, T 1 , control passes to step  610 . 
     At step  610 , controller  502  determines if the current measurement of signal quality, SQ(4), is better than the previous measurement of signal quality, SQ(3). If it is, which indicates that the signal quality is still unsatisfactory but that the user&#39;s movement helped, then control passes to step  611 . If the test fails, which indicates that the user&#39;s movement actually hurt the signal quality, then control passes to step  612 . Because SQ(4) is less than SQ(3), control passes to step  612 . 
     At step  612 , controller  502  advantageously generates a message that: (1) indicates that the user&#39;s movement to improve the signal quality actually hurt the signal quality, and (2) directs the user of wireless terminal  303  to move a short distance in the direction opposite just moved. The message is advantageously a pre-recorded or synthesized audible message that is perceivable and understandable by the user of wireless terminal  303 . Controller  502  then outputs the message to summer  504  where it is advantageously inserted, in well-known fashion, into the downlink audio channel that is being transmitted to wireless terminal  303 . 
     Alternatively, the message is a control message that that: (1) indicates that the user&#39;s movement to improve the signal quality actually hurt the signal quality, and (2) directs the user of wireless terminal  303  to move a short distance in the direction opposite just moved. In this case, controller  502  outputs the message to summer  504  wherein summer  504  inserts the control message into the downlink control message stream, in well-known fashion. After step  612 , control passes to step  606 . 
     At step  606 , controller  502  advantageously increments the counter, n, by one to n=5. 
     At step  607 , controller  502  receives a measurement of signal quality, SQ(5), of the uplink signal received from wireless terminal  303 , with the assistance of threshold detector  501 , as described above. Advantageously, the measurement of signal quality, SQ(5), is delayed until the user of wireless terminal  303  has received the most recently transmitted message and has had an opportunity to move. 
     At step  608 , controller  502  determines if the current measurement of signal quality, SQ(5), is satisfactory. Because it can be seen from the graph in FIG. 7 that SQ(5) is not above the threshold, T 1 , control passes to step  610 . 
     At step  610 , controller  502  determines if the current measurement of signal quality, SQ(5), is better than the previous measurement of signal quality, SQ(4). Because SQ(5) is better than SQ(4), control passes to step  611 . 
     At step  611 , controller  502  advantageously generates a message that: (1) indicates that the user&#39;s movement to improve the signal quality helped but is not sufficient, and (2) directs the user of wireless terminal  303  to move a short distance further in the direction just moved. The message is advantageously a pre-recorded or synthesized audible message that is perceivable and understandable by the user of wireless terminal  303 . Controller  502  then outputs the message to summer  504  where it is advantageously inserted, in well-known fashion, into the downlink audio channel that is being transmitted to wireless terminal  303 . 
     Alternatively, the message is a control message that that: (1) indicates that the user&#39;s movement to improve the signal quality helped but is not sufficient, and (2) directs the user of wireless terminal  303  to move a short distance further in the direction just moved. In this case, controller  502  outputs the message to summer  504  wherein summer  504  inserts the control message into the downlink control message stream, in well-known fashion. After step  611 , control passes to step  606 . 
     At step  606 , controller  502  advantageously increments the counter, n, by one to n=6. 
     At step  607 , controller  502  receives a measurement of signal quality, SQ(6), of the uplink signal received from wireless terminal  303 , with the assistance of threshold detector  501 , as described above. Advantageously, the measurement of signal quality, SQ(6), is delayed until the user of wireless terminal  303  has received the most recently transmitted message and has had an opportunity to move. 
     At step  608 , controller  502  determines if the current measurement of signal quality, SQ(5), is satisfactory. Because it can be seen from the graph in FIG. 7 that SQ(6) is above the threshold, T 1 , control passes to step  609 . 
     At step  609 , controller  502  advantageously generates a message that indicates that wireless terminal  303  has exited the fade and that the call is no longer in danger of being dropped. The message is advantageously a pre-recorded or synthesized audible message that is perceivable and understandable by the user of wireless terminal  303 . Controller  502  then outputs the message to summer  504  where it is advantageously inserted, in well-known fashion, into the downlink audio channel that is being transmitted to wireless terminal  303 . 
     Alternatively, the message is a control message that that indicates that wireless terminal  303  has exited the fade and that the call is no longer in danger of being dropped. In this case, controller  502  outputs the message to summer  504  wherein summer  504  inserts the control message into the downlink control message stream, in well-known fashion. 
     Simultaneously, controller  502  advantageously generates a second message that indicates that indicates that wireless terminal  303  has exited the fade and that the call is no longer in danger of being dropped. Advantageously, the second message is advantageously a pre-recorded or synthesized audible message that is perceivable and understandable by a human. Controller  502  then outputs the second message to summer  503  where it is advantageously inserted, in well-known fashion, into the uplink audio channel that is being transmitted to wireless switching center  301  on lead  306 . From step  609 , control passes to step  606 . 
     At step  606 , controller  502  advantageously increments the counter, n, by one to n=6, and the process continues until the call is terminated by the parties to the call. It will be clear to those skilled in the art how to make and use base station  302  and channel quality processor  410 . 
     Returning to FIG. 5, summer  503  and summer  504  are capable of receiving audible messages or control messages or both from controller  502  and of inserting them into the appropriate audio channel or control message stream, respectively. It will be clear to those skilled in the art how to make and use base station  302  and channel quality processor  410 . 
     FIG. 8 depicts a block diagram of a first illustrative embodiment of wireless terminal  303  that accepts control messages transmitted by base station  302  in the downlink control message stream and that generates and outputs pre-recorded or synthesized audible messages that are perceivable and understandable by the user of wireless terminal  303 . Wireless terminal  303  advantageously comprises: terminal processor  801 , display  802 , keypad  803 , transceiver  804 , antenna  805 , microphone  806 , speaker  807 , summer  808  and warning generator  809 . 
     Terminal processor  801 , display  802 , keypad  803 , transceiver  804 , antenna  805 , microphone  806  and speaker  807  are all made and used in well-known fashion. Terminal processor  801  is advantageously an appropriately-programmed general-purpose computer or hardwired special-purpose computer that is capable of detecting control messages in the downstream control message stream and of transmitting an indicium of those control messages to warning generator  809 . Advantageously, warning generator  809  is capable of receiving four different messages and of outputting to summer  808  pre-recorded or synthesized audible messages that are perceivable and understandable by the user of wireless terminal  303 . 
     The first message is generated by the control message transmitted in step  605  and: (1) indicates that wireless terminal  303  has entered a fade and that the call is in danger of being dropped, and (2) directs the user of wireless terminal  303  to move a short distance in one direction, preferably the direction from which the user just came. 
     The second message is generated by the control message transmitted in step  609  and indicates that wireless terminal  303  has exited the fade and that the call is no longer in danger of being dropped. 
     The third message is generated by the control message transmitted in step  611  and: (1) indicates that the user&#39;s movement to improve the signal quality helped but is not sufficient, and (2) directs the user of wireless terminal  303  to move a short distance further in the direction just moved. 
     The fourth message is generated by the control message transmitted in step  612  and: (1) indicates that the user&#39;s movement to improve the signal quality actually hurt the signal quality, and (2) directs the user of wireless terminal  303  to move a short distance in the direction opposite just moved. 
     Summer  808  inserts the audible message output from warning generator  809  into signal output through microphone  807 . It will be clear to those skilled in the art how to make wireless terminal  303  in accordance with the illustrative embodiment in FIG.  8 . 
     It will be clear to those skilled in the art that a signal quality meter in wireless terminal  303  can make the necessary signal quality measurements needed to ascertain when wireless terminal  303  is in a fade, or leaving a fade, or going further into the fade and that warning generator  809  can be driven my the internal signal quality meter rather than by control messages from the base station. In other words, it will be clear to those skilled in the art how to make and use wireless terminals in accordance with the present invention that are entirely self-contained in terms of measuring signal quality and providing warnings and feedback to the user and without assistance from a base station or other wireless telecommunications infrastructure. 
     FIG. 9 depicts a block diagram of a first illustrative embodiment of wireless terminal  303  that accepts control messages transmitted by base station  302  in the downlink control message stream and that generates and outputs pre-recorded or synthesized audible messages that are perceivable and understandable by the user of wireless terminal  303 . Wireless terminal  303  advantageously comprises: terminal processor  901 , display  902 , keypad  903 , transceiver  904 , antenna  905 , microphone  906 , speaker  907 , visual indicator  908 , visual indicator  909 , visual indicator  910 , visual indicator  911  and warning generator  912 . 
     Terminal processor  901 , display  902 , keypad  903 , transceiver  904 , antenna  905 , microphone  906  and speaker  907  are all made and used in well-known fashion. Terminal processor  901  is advantageously capable of detecting control messages in the downstream control message stream and of transmitting an indicium of those control messages to warning generator  912 . Advantageously, warning generator  912  is capable of receiving four different messages and of illuminating visual indicator  908 , visual indicator  909 , visual indicator  910  and/or visual indicator  911 , in accordance with each of the four control message. Each of visual indicator  908 , visual indicator  909 , visual indicator  910  and visual indicator  911  are illustratively light-emitting diodes (“LEDs”). 
     The first message is generated by the control message transmitted in step  605  and: (1) indicates that wireless terminal  303  has entered a fade and that the call is in danger of being dropped, and (2) directs the user of wireless terminal  303  to move a short distance in one direction, preferably the direction from which the user just came. 
     The second message is generated by the control message transmitted in step  609  and indicates that wireless terminal  303  has exited the fade and that the call is no longer in danger of being dropped. 
     The third message is generated by the control message transmitted in step  611  and: (1) indicates that the user&#39;s movement to improve the signal quality helped but is not sufficient, and (2) directs the user of wireless terminal  303  to move a short distance further in the direction just moved. 
     The fourth message is generated by the control message transmitted in step  612  and: (1) indicates that the user&#39;s movement to improve the signal quality actually hurt the signal quality, and (2) directs the user of wireless terminal  303  to move a short distance in the direction opposite just moved. 
     It is to be understood that the above-described embodiments are merely illustrative of the invention and that many variations may be devised by those skilled in the art without departing from the scope of the invention. It is therefore intended that such variations be included within the scope of the following claims and their equivalents.