CA2235231A1 - System and software method of operation of a radio data base station - Google Patents
System and software method of operation of a radio data base station Download PDFInfo
- Publication number
- CA2235231A1 CA2235231A1 CA002235231A CA2235231A CA2235231A1 CA 2235231 A1 CA2235231 A1 CA 2235231A1 CA 002235231 A CA002235231 A CA 002235231A CA 2235231 A CA2235231 A CA 2235231A CA 2235231 A1 CA2235231 A1 CA 2235231A1
- Authority
- CA
- Canada
- Prior art keywords
- signal
- packet
- busy
- rdbs
- beginning portion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Landscapes
- Mobile Radio Communication Systems (AREA)
Abstract
System and software method of operation of a radio data base station (RDBS). Two RDBS (12 and 14) individually transmits and receives signals on a common frequency. A wireless terminal (10) transmits a packet having at least a station identifier signal (56) identifying a RDBS. The packet is received at both RDBSs (12 and 14). Both RDBSs detect a beginning portion of the packet, set a busy bit and transmit a busy signal. Both RDBSs (12 and 14) determine whether the beginning portion has a signal strength greater than a threshold. If the beginning portion is less than the threshold, the RDBS clears the busy signal. If the beginning portion is greater than the threshold, the RDBS decodes the station identifier signal (56). If the station identifier signal (56) does not identify the RDBS, the RDBS clears the busy signal previously set. If the station identifier signal (56) identifies the RDBS, the RDBS continues to transmit the busy signal until the entire packet is received.
Description
CA 0223~231 1998-04-17 Express Mail No. EH914491896US PD05763AV
SYSTEM AND SOF~WARE METHOD OF OPERATION
OF A RADIO DATA BASE STATION
l~ield of the Invention This invention relates generally to a system of a radio base station and a software method for control of a radio data base station, for example, for reducing the "sensitivity" of a radio data base station without the need for hardware attenuators or a degradation of the actual signal.
Background of the Invention In a radio data system, sometimes it is the case that the radio data base station (RDBS) receiver is much more sensitive than the wireless receiver, in which case it is desirable to attenuate the receive signal in the RDBS to balance the uplink and the downlink channels. The uplink channel is a communication from the 15 wireless terrninal to the RDBS ~md the downlink channel is conl~ mication from the RDBS to the wireless terrninal. This is particularly important in a situation with a tight frequency reuse pattern, where the RDBS does not want to receive the signal intended for another RDBS on the same frequency.
When a ROBS detects a beginning portion of a packet (uplink packet) in an 20 uplink channel, it sets a busy signal (i.e., sets a busy bit and transrnits a busy signal to other RDBSs) in a downlink channel in(li~:~ting that the uplink channel is busy.
The busy signal is operative for the duration of the uplink packet. During this busy condition, other wireless termin~lc registered on the cell are not ~lll~iL~d to start using the uplink channel until the wireless terrninal currently using the uplink25 ch~nnel has completed tr~n~mi~ting the uplink packet. When the uplink packet is completely received, the RDBS controller clears the busy signal.
CA 0223~231 1998-04-17 Employing such a method, as used in DataTAC infrastructure which is available from Motorola Inc., the RDBS controller may incorrectly detect the beginning portion of the uplink packet due to co-channel interference. For example, RDBS A and RDBS B transmit and receive uplink packets on the same 5 frequency. A wireless terminal transmits an uplink packet to RDBS A. RDBS A
receives a strong signal and RDBS B receives a weak signal. Both RDBS A and RDBS B individually transmit busy signals to the other wireless terrninals.
As described above, a RDBS controller will indicate that an uplink channel is busy even if the uplink packet is not intended for that particular RDBS. When10 multiple RDBSs receive an uplink packet, the RDBSs decode the uplink packet and forward the uplink packet to their respective RDBS controller for processing. This means that multiple cells "busy out" the uplink channel even if the wireless tt-rmin~l is not operating on its cell (i.e., creating a "false busy" situation). The RDBScontinues to transmit the "false busy" signal until the entire uplink packet is received 15 at the intended RDBS. Creating a "false busy" situation restricts the uplink throughput and places an unnecessary proces.cing burden on the RDBS controller (rejecting duplicate messages).
The method currently used in the state-of-the-art to prevent multiple RDBSs (e.g., RDBS B) from picking up signals intended for another RDBS (e.g., RDBS
20 A) is to m~nu~lly tune the hardware receive attenuators in the RDBSs so that they are not sensitive enough to receive signals from wireless termin~lc as far away as another cell using the same frequency. This is a time concllming manual process that requires a site visit and involves extra hardware components in the RDBS.
As a result of the time consuming manual process and the extra hardware 25 attenuators used to prevent the RDBS receiver from being much more sensitive than the wireless termin~l receiver, and the prolonged "false busy" signals when multiple CA 0223~231 1998-04-17 RDBSs receive the same uplink packet, there exists a need for a system and a method that reduces the time, the cost and the "false busy" signals without the need for hardware attenuators or a degradation of the actual signal.
A preferred embodiment of the invention, is now described, by way of 5 example only, with reference to the drawings.
Brief I)escription of the Drawings The features of the present invention are set forth with particularity in the appended claims. Preferred embodiments of the invention are now described, by 10 way of example only, with reference to the accompanying drawings in which:
FIG. 1 is a diagram of a RDBS according to a preferred embodiment of the invention;
FIG. 2 is a cell diagram for purposes of explanation of the ~ fell~d embodiment of the invention;
FIG. 3 is a diagram of an uplink packet according to the preferred embodiment of the invention;
FIG. 4 is a flow chart of a busy control mechanism according to the prefelled embodiment of the invention;
FIG. 5 is a flow chart of a busy control mechanism according to a first 20 ~lt~rn~ive embodiment of the invention;
FIG. 6 is a flow chart of a busy control mechanism according to a second ~ltern~tive embodiment of the invention; and FIG. 7 is a flow chart of a busy control mechanism according to a third tive embodiment of the invention.
CA 0223~231 1998-04-17 It will be appreciated that for simplicity and clarity of illustration, elementsshown in the figures have not necessarily been drawn to scale. Where considered a~plo~ fiate, reference numerals have been repeated among the figures to indicate corresponding elements.
s Detailed Description of the Preferred Embodiment A software attenuation method, now described, elimin:lt~s the need for hal.lwi~e attenuators and m~int:linc the received signal quality. The software attenuation method is easily controlled either automatically or remotely.
A radio data system may have either a single frequency reuse pattern or a multiple frequency reuse pattern. The radio frequency (RF) design of the radio data system is similar in nature to cellular voice. ~ imitto~l RF spectrum requires frequencies to be reused. The amount of frequency reuse is dependent on the available spectrum, required system capacily and RF limitations (terrain; maximum 15 tolerated carrier-to-interference ratio; device power). Radio data systems typically require at least a twelve-frequency reuse pattern. This frequency reuse pattern is needed to provide in-building coverage for low power devices such as the PM100 Personal Computer Memory Card International Association (PCMCIA) slot radio data- link access protocol (RD-I,AP) RF modem which is available from Motorola 20 Inc. This design forces a radio data base station (RDBS) deployment of close proximity stations with low uplink channel power.
It is possible for two or more RDBSs on the same frequency to receive an uplink packet from a wireless terminal registered on only one of the RDBSs. Thiscould occur if the wireless terminal is being used in a tall building or operating near 25 the fringe of a cell. It is desirable to prevent remote RDBSs from detecting the presence of a signal transmitted by a wireless terminal which is not intended for that particular RDBS. This is to prevent a "false busy", which wastes precious air time.
FIG. 1 is a diagram of a RDBS 12 according to a preferred embodiment of the invention. RDBSs are located at radio sites to provide the required radio S coverage. This integrated RDBS 12 comprises at least a RF transceiver 28 and aRDBS controller 30. The transceiver has at least a signal output 29. The RDBS
controller 30 fùrther comprises a busy signal generator 32, a station identifiercomyala~or 34 having at least a ~predetermined station identification 36, a signal detector 38, a signal strength memory unit 40 and a predetermined threshold value 42. The busy signal generator 32 is coupled to the RF transceiver 28. The station ~ PntifiP.r comparator 34 and the signal detector 38 are individually coupled to the busy signal generator 32 and are individually coupled to the RF transceiver 28. The signal strength memory unit 40 has a first input 41 coupled to the predeterminedthreshold value, a second input 43 coupled to the RF transceiver and an output 45 15 coupled to the busy signal generator. It will be understood by one skilled in the art that the RDBS controller is preferably implemented in a microprocessor, digital signal processor, micro-controller or combination of such elements and that the various elements 32, 34, 36, 38, 40 and 42 are preferably implemented in software but may be implemented as haldwale circuits or as some combination of hardware 20 and software. All such embodiments are inch1clPfl within the software method and the system of the present invention.
The RF transceiver 28 sends data over radio frequencies between the RDBS
controller 30 and the wireless terminals. The RDBS controller 30 implements a RD-LAP RF protocol. (The RD-LAP protocol is used to transport data over 25 narrow-band radio frequencies'~. Wireless terminals are devices used by subscribers to send and receive data over an infrastructure (e.g., a DataTAC
infrastructure available from Motorola Inc.). Wireless terminals can roam throughout the radio coverage area of the infrastructure. Each wireless termin~lsupported by the infrastructure comprises two distinct components: a radio packet modem and data terrninal equipment. The radio packet modem transmits and 5 receives data packets over a radio channel. The data terminal equipment provides the user interface functions of the wireless channel.
A RDBS 12 in a digital sense multiple access (DSMA) radio data system detects the presence of an uplink packet from a wireless terminal and sets a busy signal (i.e., sets a busy bit and transmits a busy signal to other RDBSs) to prevent 10 other wireless t~rmin~l~ from tr~n.cmitting on a particular uplink channel at the same time. Such DSMA radio systems are available from various m~nnf~tllrers such as Motorola Inc. under various trade names such as DataTAC. To do this, the RDBS
controller 30 usually detects a beginning portion of the uplink packet, such as a symbol synchlol1ization signal (e.g., a regular repetitive pattern) whereupon it sets 15 the uplink channel busy.
~ IG. 2 is a cell diagrarn for purposes of explanation of the preferred embodiment of the invention. In FIG. 2, a first RDBS 12 and a second RDBS 14 are both tr:~n.~mitting and receiving signals on a comrnon frequency (e.g., frequency 1). A wireless terrninal 10 sends a packet in an uplink channel (uplink packet) 20 having at least a station identifier signal identifying that the uplink packet is intended for the first RDBS 12. The uplink packet, however, is received and decoded at both the first RDBS 12 and the second RDBS 14. As a result, the first RDBS 12 and the second RDBS 14 transmit a busy signal in a downlink channel indicating that the uplink channel is busy. Both the first RDBS 12 and the second RDBS 14 25 have made their cell busy, thus preventing other wireless terminals from using their cell. After the first RDBS 12 and the second RDBS 14 set their busy signal in the CA 0223~231 1998-04-17 downlink channel respectively, the first RDBS 12 and the second RDBS 14 receive and decode the station identifier signal. Since the station identifier signal matches the predetermined station identification stored at the first RDBS 12 and does not match the predetermined station identification stored at the second RDBS 14, the5 first RDBS 12 continues to transmit the busy signal in the downlink channel, receives the uplink packet in its entirety and clears its busy signal at the next opportunity. The second RDBS 14, however, clears its busy signal in the downlink channel immediately after the second RDBS 14 decodes the station identifier signal and identifies that the station identifier signal does not match its 10 predetermined station identification. Thus, the station identifier signal informs remote RDBSs (e.g., the second RDBS) to clear their busy signal. Thus, a RDBS
can set a busy signal in the downlink channel if the uplink packet has been sentfrom a wireless terminal 10 registered on its cell (i.e., "intelligent busy"). The RDBS 12 can also discard any message sent from a wireless terminal 10 not 15 registered on its cell (i.e., "message discard").
FIG. 3 is a diagram of an uplink packet according to the preferred embodiment of the invention (e.g., an uplink packet at 19.2 baud in a DataTAC
radio data system). The RDBS controller 30 receives a beginning portion (e.g., asymbol synchronization signal 52) of the uplink packet from a wireless terminal 10.
20 The RDBS controller 30 decodes the beginning portion of the uplink packet andsets the uplink channel busy by transmitting a busy signal in a downlink channel.
The RDBS 12 transmits the busy signal to other wireless terminals. The RDBS 12 continues to transmit the busy signal to the other wireless terrnin:~ls if a frame synchronization signal 54 of the uplink packet is received within a predetermined 25 time period (e.g., approximately 50 ms). If the RDBS controller does not receive CA 0223~231 1998-04-17 the frame synchronization signal 54 within the predetermined time period, the RDBS 12 clears the busy signal and searches for a start of another uplink packet.
FIG. 4 is a flow chart of a busy control mechanism according to the plefelled embodiment of the invention at step 62. The RDBS 12 detects a 5 beginning portion of an uplink packet at step 64. The RDBS 12 measures a received signal strength indicator (RSSI) at step 65 based on the signal strength of the beginning portion of the uplink packet. The RDBS 12 determines if the RSSI
of the beginning portion of the uplink packet exceeds a predetermined threshold value 42 at step 66. If the RSSI of the beginning portion of the uplink packet is 10 less than the predetermined threshold value 42, the RDBS 12 searches for a start of another uplink packet at step 64. If the RSSI of the beginning portion of the uplink packet exceeds the predetermined threshold value 42, the RDBS 12 sets a busy signal at step 68 in a downlink channel indicating that the uplink channel is busy.
The RDBS 12 receives the uplink packet in its entirety at step 69 and clears the busy 15 signal at step 70. The busy control mech:lni~m for the uplink packet that wascurrently received by the RDBS ends at step 71 and the RDBS begins searching fora start of another uplink packet.
FIG. S is a flow chart of a busy control mechanism according to a first alternative embodiment of the invention at step 72. The RDBS 12 detects a 20 beginning portion of an uplink packet at step 74 having a signal strength. The RDBS 12 sets a busy signal at step 76 in a downlink channel indicating that the uplink channel is busy upon detection of the beginning portion of the uplink packet.
The RDBS 12 measures a received signal strength indicator (RSSI) at step 77 based on the signal strength of the beginning portion of the uplink packet. The RDBS 12 25 determines whether the RSSI of the beginning portion of the uplink packet is greater than a predetermined threshold value 42 at step 78. If the RSSI of the CA 0223~231 1998-04-17 beginning portion of the packet is less than the predeterrnined threshold value 42, the RDBS 12 clears the busy signal at step 80 and searches for a start of another uplink packet (e.g., symbol synchronization signal). If the RSSI of the beginning portion of the uplink packet is greater than the predetermined threshold value 42, the RDBS 12 continues to transmit the busy signal until the uplink packet is received in its entirety at step 81 and clears the busy signal at step 82. The busy control mechanism for the uplink packet that was currently received by the RDBS
ends at step 83 and the RDBS begins searching for a start of another uplink packet.
FIG. 6 is a flow chart of a busy control mechanism according to a second 10 alternative embodiment of the invention. The RDBS starts the busy control mechanism at step 84. The RDBS 12 detects a beginning portion of an uplink packet at step 86. Based on detec~ing the beginning portion of the uplink packet at step 86, the RDBS 12 sets a busy signal at step 88 in a downlink channel indicating that the uplink channel is busy. The RDBS 12 decodes a received station identifier 15 signal from the uplink packet at step 90. The RDBS 12 compares the received station identifier signal 56 with a predetermined station identification 36 for the RDBS 12 at step 92. The RDBS 12 clears the busy signal at step 94 if the received station identifier signal 56 does not match the predeterrnined station identification 36 of the RDBS and searches for a start of another uplink packet. If the received 20 station itlentifier signal 56 matches the predeterrnined station identification 36 of the RDBS 12 at step 92, the RDBS 12 receives the uplink packet in its entirety at step 96 and clears the busy signal at step 98. The RDBS 12 ends the busy control mech~ni~m for the uplink packet that was currently received by the RDBS at step 100 and the RDBS begins searching for a start of another uplink packet.
FIG. 7 is a flow chart of a busy control mechanism according to a third alternative embodiment of the invention. The RDBS 12 starts a busy control CA 0223~231 1998-04-17 mechanism at step 104. The RDBS controller 30 detects a beginning portion of an uplink packet at step 106. The RDBS controller 30 sets a busy signal at step 108and measures the RSSI of the beginning portion of the uplink packet at step 109.The RDBS controller deterrnines whether the beginning portion of the uplink packet (e.g., symbol synchronization signal 52) has a signal strength greater than a predetelmined threshold value 42 at step 110. If the beginning portion of the uplink packet 52 has a signal strength less than or equal to the predetermined threshold value 42, the RDBS 12 clears the busy signal at step 112 and searches for a start of another uplink packet. If the beginning portion of the uplink packet 52 has a signal 10 strength greater than the predetermined threshold value 42, the RDBS 12 deterrnines whether a frame synchronization signal 54 has been detected before apredetermined time at step 114, in which the predeterrnined time is dependent on a protocol.
If the frame synchronization signal 54 is not detected before the 15 predetermined time, the RDBS controller 30 clears the busy signal at step 112 and searches for a start of another uplink packet. If the frame synchronization signal 54 is detected within the predetermined time, the RDBS controller 30 deterrnines whether a station identifier signal 56 of the uplink packet identifies the RDBS at step 116.
If the station identifier signal 56 in the uplink packet does not identify the RDBS 12, the RDBS 12 clears the busy signal at step 112 and searches for a startof another uplink packet. If the station identifier signal 56 does identify the RDBS
12, a packet header is received at the RDBS at step 117 and the RDBS 12 determines whether the packet header 58 is received correctly at step 118.
If the packet header 58 is not received correctly at step 118, the RL',BS 12 waits for the RSSI of the uplink si~nal to drop below an "exit threshold" 42 or until CA 0223~231 1998-04-17 the maximum uplink packet length (e.g., time) is reached at step 120. After one of these events occurs, the RDBS 12 clears the busy signal at step 112 and searchesfor a start of another uplink packet. If the packet header 58 is received correctly at step 118, the RDBS 12 receives the uplink packet in its entirety at step 122 and5 clears the busy signal at step 123. The busy control mechanism for the uplink packet that was currently received by the RDBS ends at step 124 and the RDBS
begins searching for a start of another uplink packet.
A problem with the current state-of-the-art, which employs a hardware attenuation method of balancing, is that the signal is degraded (by the manually10 tuned receive attenuator) to an extent that the Rl:)BS controller cannot detect the relevant pattern (e.g., symbol synchronization signal). The software attenuationmethod, as described above by way of example only, involves a predetermined threshold value 42 which the beginning portion of the uplink packet (e.g., a symbol synchronization signal or other app.opliate pattern) must exceed before the RDBS15 controller 30 declares the uplink channel busy. This predetermined threshold value 42 could easily be tuned remotely (e.g., as an simple network management protocol variable) or automatically by using some method not disclosed herein.
Further, there is a "window of vulnerability" between the time when a first wireless terminal 10 transmits and when the RDBS 12 transmits that the channel is 20 busy to other wireless te~lmin~lc. After the first wireless terminal 10 transmits an uplink packet to the RDBS 12 but before the RDBS 12 transmits that the uplink channel is busy to other wireless terminals, a second wireless terminal may start to transmit to the Rr)BS 12 as well. If this happens, a collision will occur between the tr~n~mi.csions from the first wireless terminal 10 and the second wireless telmin~l 25 because during the "window of vulnerability", the second wireless terminal has not yet received a busy signal indicating that the uplink channel is busy from the RDBS
CA 0223~231 1998-04-17 12. Thus, the larger the "window of vulnerability", the greater the potential for collisions.
The software attenuation method, as described above by example only, shortens the "window of vulnerability". The software attenuation method quickly 5 detects that an uplink channel is busy and communicates this to the RDBSs without delay (e.g., the ~DBS receives a beginning portion of the packet and imm~ ely transmits a busy signal). After the RDBS 12 receives the beginning portion of an uplink packet (e.g., the symbol synchronization signal 52), the RDBS 12 measures the RSSI of the beginning portion of the uplink packet and 10 compares the measurement with a predetermin~ threshold value 42. If the RSSI
of the beginning portion of the uplink packet exceeds the predeterrnined threshold value 42, the RDBS 12 continues to transmit the busy signal. If the RSSI of the beginning portion of the uplink packet does not exceed the predetermined threshold value 42, the RDBS 12 clears the busy signal and searches for a start of 15 another upli.1k packet. The software attenuation method is also applicable if the RDBS 12 waits to determine if the RSSI of the beginning portion of the uplink packet exceeds the predetermined tnreshold value 42 before setting the busy signal.
While the invention has been described in conjunction with a specific 20 embodiment thereof, it is evident that many alterations, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Thus, it should be understood that the invention is not limited by the foregoing description, but embraces all such alterations, modifications and variations in accordance with the spirit and scope of the appended claims.
SYSTEM AND SOF~WARE METHOD OF OPERATION
OF A RADIO DATA BASE STATION
l~ield of the Invention This invention relates generally to a system of a radio base station and a software method for control of a radio data base station, for example, for reducing the "sensitivity" of a radio data base station without the need for hardware attenuators or a degradation of the actual signal.
Background of the Invention In a radio data system, sometimes it is the case that the radio data base station (RDBS) receiver is much more sensitive than the wireless receiver, in which case it is desirable to attenuate the receive signal in the RDBS to balance the uplink and the downlink channels. The uplink channel is a communication from the 15 wireless terrninal to the RDBS ~md the downlink channel is conl~ mication from the RDBS to the wireless terrninal. This is particularly important in a situation with a tight frequency reuse pattern, where the RDBS does not want to receive the signal intended for another RDBS on the same frequency.
When a ROBS detects a beginning portion of a packet (uplink packet) in an 20 uplink channel, it sets a busy signal (i.e., sets a busy bit and transrnits a busy signal to other RDBSs) in a downlink channel in(li~:~ting that the uplink channel is busy.
The busy signal is operative for the duration of the uplink packet. During this busy condition, other wireless termin~lc registered on the cell are not ~lll~iL~d to start using the uplink channel until the wireless terrninal currently using the uplink25 ch~nnel has completed tr~n~mi~ting the uplink packet. When the uplink packet is completely received, the RDBS controller clears the busy signal.
CA 0223~231 1998-04-17 Employing such a method, as used in DataTAC infrastructure which is available from Motorola Inc., the RDBS controller may incorrectly detect the beginning portion of the uplink packet due to co-channel interference. For example, RDBS A and RDBS B transmit and receive uplink packets on the same 5 frequency. A wireless terminal transmits an uplink packet to RDBS A. RDBS A
receives a strong signal and RDBS B receives a weak signal. Both RDBS A and RDBS B individually transmit busy signals to the other wireless terrninals.
As described above, a RDBS controller will indicate that an uplink channel is busy even if the uplink packet is not intended for that particular RDBS. When10 multiple RDBSs receive an uplink packet, the RDBSs decode the uplink packet and forward the uplink packet to their respective RDBS controller for processing. This means that multiple cells "busy out" the uplink channel even if the wireless tt-rmin~l is not operating on its cell (i.e., creating a "false busy" situation). The RDBScontinues to transmit the "false busy" signal until the entire uplink packet is received 15 at the intended RDBS. Creating a "false busy" situation restricts the uplink throughput and places an unnecessary proces.cing burden on the RDBS controller (rejecting duplicate messages).
The method currently used in the state-of-the-art to prevent multiple RDBSs (e.g., RDBS B) from picking up signals intended for another RDBS (e.g., RDBS
20 A) is to m~nu~lly tune the hardware receive attenuators in the RDBSs so that they are not sensitive enough to receive signals from wireless termin~lc as far away as another cell using the same frequency. This is a time concllming manual process that requires a site visit and involves extra hardware components in the RDBS.
As a result of the time consuming manual process and the extra hardware 25 attenuators used to prevent the RDBS receiver from being much more sensitive than the wireless termin~l receiver, and the prolonged "false busy" signals when multiple CA 0223~231 1998-04-17 RDBSs receive the same uplink packet, there exists a need for a system and a method that reduces the time, the cost and the "false busy" signals without the need for hardware attenuators or a degradation of the actual signal.
A preferred embodiment of the invention, is now described, by way of 5 example only, with reference to the drawings.
Brief I)escription of the Drawings The features of the present invention are set forth with particularity in the appended claims. Preferred embodiments of the invention are now described, by 10 way of example only, with reference to the accompanying drawings in which:
FIG. 1 is a diagram of a RDBS according to a preferred embodiment of the invention;
FIG. 2 is a cell diagram for purposes of explanation of the ~ fell~d embodiment of the invention;
FIG. 3 is a diagram of an uplink packet according to the preferred embodiment of the invention;
FIG. 4 is a flow chart of a busy control mechanism according to the prefelled embodiment of the invention;
FIG. 5 is a flow chart of a busy control mechanism according to a first 20 ~lt~rn~ive embodiment of the invention;
FIG. 6 is a flow chart of a busy control mechanism according to a second ~ltern~tive embodiment of the invention; and FIG. 7 is a flow chart of a busy control mechanism according to a third tive embodiment of the invention.
CA 0223~231 1998-04-17 It will be appreciated that for simplicity and clarity of illustration, elementsshown in the figures have not necessarily been drawn to scale. Where considered a~plo~ fiate, reference numerals have been repeated among the figures to indicate corresponding elements.
s Detailed Description of the Preferred Embodiment A software attenuation method, now described, elimin:lt~s the need for hal.lwi~e attenuators and m~int:linc the received signal quality. The software attenuation method is easily controlled either automatically or remotely.
A radio data system may have either a single frequency reuse pattern or a multiple frequency reuse pattern. The radio frequency (RF) design of the radio data system is similar in nature to cellular voice. ~ imitto~l RF spectrum requires frequencies to be reused. The amount of frequency reuse is dependent on the available spectrum, required system capacily and RF limitations (terrain; maximum 15 tolerated carrier-to-interference ratio; device power). Radio data systems typically require at least a twelve-frequency reuse pattern. This frequency reuse pattern is needed to provide in-building coverage for low power devices such as the PM100 Personal Computer Memory Card International Association (PCMCIA) slot radio data- link access protocol (RD-I,AP) RF modem which is available from Motorola 20 Inc. This design forces a radio data base station (RDBS) deployment of close proximity stations with low uplink channel power.
It is possible for two or more RDBSs on the same frequency to receive an uplink packet from a wireless terminal registered on only one of the RDBSs. Thiscould occur if the wireless terminal is being used in a tall building or operating near 25 the fringe of a cell. It is desirable to prevent remote RDBSs from detecting the presence of a signal transmitted by a wireless terminal which is not intended for that particular RDBS. This is to prevent a "false busy", which wastes precious air time.
FIG. 1 is a diagram of a RDBS 12 according to a preferred embodiment of the invention. RDBSs are located at radio sites to provide the required radio S coverage. This integrated RDBS 12 comprises at least a RF transceiver 28 and aRDBS controller 30. The transceiver has at least a signal output 29. The RDBS
controller 30 fùrther comprises a busy signal generator 32, a station identifiercomyala~or 34 having at least a ~predetermined station identification 36, a signal detector 38, a signal strength memory unit 40 and a predetermined threshold value 42. The busy signal generator 32 is coupled to the RF transceiver 28. The station ~ PntifiP.r comparator 34 and the signal detector 38 are individually coupled to the busy signal generator 32 and are individually coupled to the RF transceiver 28. The signal strength memory unit 40 has a first input 41 coupled to the predeterminedthreshold value, a second input 43 coupled to the RF transceiver and an output 45 15 coupled to the busy signal generator. It will be understood by one skilled in the art that the RDBS controller is preferably implemented in a microprocessor, digital signal processor, micro-controller or combination of such elements and that the various elements 32, 34, 36, 38, 40 and 42 are preferably implemented in software but may be implemented as haldwale circuits or as some combination of hardware 20 and software. All such embodiments are inch1clPfl within the software method and the system of the present invention.
The RF transceiver 28 sends data over radio frequencies between the RDBS
controller 30 and the wireless terminals. The RDBS controller 30 implements a RD-LAP RF protocol. (The RD-LAP protocol is used to transport data over 25 narrow-band radio frequencies'~. Wireless terminals are devices used by subscribers to send and receive data over an infrastructure (e.g., a DataTAC
infrastructure available from Motorola Inc.). Wireless terminals can roam throughout the radio coverage area of the infrastructure. Each wireless termin~lsupported by the infrastructure comprises two distinct components: a radio packet modem and data terrninal equipment. The radio packet modem transmits and 5 receives data packets over a radio channel. The data terminal equipment provides the user interface functions of the wireless channel.
A RDBS 12 in a digital sense multiple access (DSMA) radio data system detects the presence of an uplink packet from a wireless terminal and sets a busy signal (i.e., sets a busy bit and transmits a busy signal to other RDBSs) to prevent 10 other wireless t~rmin~l~ from tr~n.cmitting on a particular uplink channel at the same time. Such DSMA radio systems are available from various m~nnf~tllrers such as Motorola Inc. under various trade names such as DataTAC. To do this, the RDBS
controller 30 usually detects a beginning portion of the uplink packet, such as a symbol synchlol1ization signal (e.g., a regular repetitive pattern) whereupon it sets 15 the uplink channel busy.
~ IG. 2 is a cell diagrarn for purposes of explanation of the preferred embodiment of the invention. In FIG. 2, a first RDBS 12 and a second RDBS 14 are both tr:~n.~mitting and receiving signals on a comrnon frequency (e.g., frequency 1). A wireless terrninal 10 sends a packet in an uplink channel (uplink packet) 20 having at least a station identifier signal identifying that the uplink packet is intended for the first RDBS 12. The uplink packet, however, is received and decoded at both the first RDBS 12 and the second RDBS 14. As a result, the first RDBS 12 and the second RDBS 14 transmit a busy signal in a downlink channel indicating that the uplink channel is busy. Both the first RDBS 12 and the second RDBS 14 25 have made their cell busy, thus preventing other wireless terminals from using their cell. After the first RDBS 12 and the second RDBS 14 set their busy signal in the CA 0223~231 1998-04-17 downlink channel respectively, the first RDBS 12 and the second RDBS 14 receive and decode the station identifier signal. Since the station identifier signal matches the predetermined station identification stored at the first RDBS 12 and does not match the predetermined station identification stored at the second RDBS 14, the5 first RDBS 12 continues to transmit the busy signal in the downlink channel, receives the uplink packet in its entirety and clears its busy signal at the next opportunity. The second RDBS 14, however, clears its busy signal in the downlink channel immediately after the second RDBS 14 decodes the station identifier signal and identifies that the station identifier signal does not match its 10 predetermined station identification. Thus, the station identifier signal informs remote RDBSs (e.g., the second RDBS) to clear their busy signal. Thus, a RDBS
can set a busy signal in the downlink channel if the uplink packet has been sentfrom a wireless terminal 10 registered on its cell (i.e., "intelligent busy"). The RDBS 12 can also discard any message sent from a wireless terminal 10 not 15 registered on its cell (i.e., "message discard").
FIG. 3 is a diagram of an uplink packet according to the preferred embodiment of the invention (e.g., an uplink packet at 19.2 baud in a DataTAC
radio data system). The RDBS controller 30 receives a beginning portion (e.g., asymbol synchronization signal 52) of the uplink packet from a wireless terminal 10.
20 The RDBS controller 30 decodes the beginning portion of the uplink packet andsets the uplink channel busy by transmitting a busy signal in a downlink channel.
The RDBS 12 transmits the busy signal to other wireless terminals. The RDBS 12 continues to transmit the busy signal to the other wireless terrnin:~ls if a frame synchronization signal 54 of the uplink packet is received within a predetermined 25 time period (e.g., approximately 50 ms). If the RDBS controller does not receive CA 0223~231 1998-04-17 the frame synchronization signal 54 within the predetermined time period, the RDBS 12 clears the busy signal and searches for a start of another uplink packet.
FIG. 4 is a flow chart of a busy control mechanism according to the plefelled embodiment of the invention at step 62. The RDBS 12 detects a 5 beginning portion of an uplink packet at step 64. The RDBS 12 measures a received signal strength indicator (RSSI) at step 65 based on the signal strength of the beginning portion of the uplink packet. The RDBS 12 determines if the RSSI
of the beginning portion of the uplink packet exceeds a predetermined threshold value 42 at step 66. If the RSSI of the beginning portion of the uplink packet is 10 less than the predetermined threshold value 42, the RDBS 12 searches for a start of another uplink packet at step 64. If the RSSI of the beginning portion of the uplink packet exceeds the predetermined threshold value 42, the RDBS 12 sets a busy signal at step 68 in a downlink channel indicating that the uplink channel is busy.
The RDBS 12 receives the uplink packet in its entirety at step 69 and clears the busy 15 signal at step 70. The busy control mech:lni~m for the uplink packet that wascurrently received by the RDBS ends at step 71 and the RDBS begins searching fora start of another uplink packet.
FIG. S is a flow chart of a busy control mechanism according to a first alternative embodiment of the invention at step 72. The RDBS 12 detects a 20 beginning portion of an uplink packet at step 74 having a signal strength. The RDBS 12 sets a busy signal at step 76 in a downlink channel indicating that the uplink channel is busy upon detection of the beginning portion of the uplink packet.
The RDBS 12 measures a received signal strength indicator (RSSI) at step 77 based on the signal strength of the beginning portion of the uplink packet. The RDBS 12 25 determines whether the RSSI of the beginning portion of the uplink packet is greater than a predetermined threshold value 42 at step 78. If the RSSI of the CA 0223~231 1998-04-17 beginning portion of the packet is less than the predeterrnined threshold value 42, the RDBS 12 clears the busy signal at step 80 and searches for a start of another uplink packet (e.g., symbol synchronization signal). If the RSSI of the beginning portion of the uplink packet is greater than the predetermined threshold value 42, the RDBS 12 continues to transmit the busy signal until the uplink packet is received in its entirety at step 81 and clears the busy signal at step 82. The busy control mechanism for the uplink packet that was currently received by the RDBS
ends at step 83 and the RDBS begins searching for a start of another uplink packet.
FIG. 6 is a flow chart of a busy control mechanism according to a second 10 alternative embodiment of the invention. The RDBS starts the busy control mechanism at step 84. The RDBS 12 detects a beginning portion of an uplink packet at step 86. Based on detec~ing the beginning portion of the uplink packet at step 86, the RDBS 12 sets a busy signal at step 88 in a downlink channel indicating that the uplink channel is busy. The RDBS 12 decodes a received station identifier 15 signal from the uplink packet at step 90. The RDBS 12 compares the received station identifier signal 56 with a predetermined station identification 36 for the RDBS 12 at step 92. The RDBS 12 clears the busy signal at step 94 if the received station identifier signal 56 does not match the predeterrnined station identification 36 of the RDBS and searches for a start of another uplink packet. If the received 20 station itlentifier signal 56 matches the predeterrnined station identification 36 of the RDBS 12 at step 92, the RDBS 12 receives the uplink packet in its entirety at step 96 and clears the busy signal at step 98. The RDBS 12 ends the busy control mech~ni~m for the uplink packet that was currently received by the RDBS at step 100 and the RDBS begins searching for a start of another uplink packet.
FIG. 7 is a flow chart of a busy control mechanism according to a third alternative embodiment of the invention. The RDBS 12 starts a busy control CA 0223~231 1998-04-17 mechanism at step 104. The RDBS controller 30 detects a beginning portion of an uplink packet at step 106. The RDBS controller 30 sets a busy signal at step 108and measures the RSSI of the beginning portion of the uplink packet at step 109.The RDBS controller deterrnines whether the beginning portion of the uplink packet (e.g., symbol synchronization signal 52) has a signal strength greater than a predetelmined threshold value 42 at step 110. If the beginning portion of the uplink packet 52 has a signal strength less than or equal to the predetermined threshold value 42, the RDBS 12 clears the busy signal at step 112 and searches for a start of another uplink packet. If the beginning portion of the uplink packet 52 has a signal 10 strength greater than the predetermined threshold value 42, the RDBS 12 deterrnines whether a frame synchronization signal 54 has been detected before apredetermined time at step 114, in which the predeterrnined time is dependent on a protocol.
If the frame synchronization signal 54 is not detected before the 15 predetermined time, the RDBS controller 30 clears the busy signal at step 112 and searches for a start of another uplink packet. If the frame synchronization signal 54 is detected within the predetermined time, the RDBS controller 30 deterrnines whether a station identifier signal 56 of the uplink packet identifies the RDBS at step 116.
If the station identifier signal 56 in the uplink packet does not identify the RDBS 12, the RDBS 12 clears the busy signal at step 112 and searches for a startof another uplink packet. If the station identifier signal 56 does identify the RDBS
12, a packet header is received at the RDBS at step 117 and the RDBS 12 determines whether the packet header 58 is received correctly at step 118.
If the packet header 58 is not received correctly at step 118, the RL',BS 12 waits for the RSSI of the uplink si~nal to drop below an "exit threshold" 42 or until CA 0223~231 1998-04-17 the maximum uplink packet length (e.g., time) is reached at step 120. After one of these events occurs, the RDBS 12 clears the busy signal at step 112 and searchesfor a start of another uplink packet. If the packet header 58 is received correctly at step 118, the RDBS 12 receives the uplink packet in its entirety at step 122 and5 clears the busy signal at step 123. The busy control mechanism for the uplink packet that was currently received by the RDBS ends at step 124 and the RDBS
begins searching for a start of another uplink packet.
A problem with the current state-of-the-art, which employs a hardware attenuation method of balancing, is that the signal is degraded (by the manually10 tuned receive attenuator) to an extent that the Rl:)BS controller cannot detect the relevant pattern (e.g., symbol synchronization signal). The software attenuationmethod, as described above by way of example only, involves a predetermined threshold value 42 which the beginning portion of the uplink packet (e.g., a symbol synchronization signal or other app.opliate pattern) must exceed before the RDBS15 controller 30 declares the uplink channel busy. This predetermined threshold value 42 could easily be tuned remotely (e.g., as an simple network management protocol variable) or automatically by using some method not disclosed herein.
Further, there is a "window of vulnerability" between the time when a first wireless terminal 10 transmits and when the RDBS 12 transmits that the channel is 20 busy to other wireless te~lmin~lc. After the first wireless terminal 10 transmits an uplink packet to the RDBS 12 but before the RDBS 12 transmits that the uplink channel is busy to other wireless terminals, a second wireless terminal may start to transmit to the Rr)BS 12 as well. If this happens, a collision will occur between the tr~n~mi.csions from the first wireless terminal 10 and the second wireless telmin~l 25 because during the "window of vulnerability", the second wireless terminal has not yet received a busy signal indicating that the uplink channel is busy from the RDBS
CA 0223~231 1998-04-17 12. Thus, the larger the "window of vulnerability", the greater the potential for collisions.
The software attenuation method, as described above by example only, shortens the "window of vulnerability". The software attenuation method quickly 5 detects that an uplink channel is busy and communicates this to the RDBSs without delay (e.g., the ~DBS receives a beginning portion of the packet and imm~ ely transmits a busy signal). After the RDBS 12 receives the beginning portion of an uplink packet (e.g., the symbol synchronization signal 52), the RDBS 12 measures the RSSI of the beginning portion of the uplink packet and 10 compares the measurement with a predetermin~ threshold value 42. If the RSSI
of the beginning portion of the uplink packet exceeds the predeterrnined threshold value 42, the RDBS 12 continues to transmit the busy signal. If the RSSI of the beginning portion of the uplink packet does not exceed the predetermined threshold value 42, the RDBS 12 clears the busy signal and searches for a start of 15 another upli.1k packet. The software attenuation method is also applicable if the RDBS 12 waits to determine if the RSSI of the beginning portion of the uplink packet exceeds the predetermined tnreshold value 42 before setting the busy signal.
While the invention has been described in conjunction with a specific 20 embodiment thereof, it is evident that many alterations, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Thus, it should be understood that the invention is not limited by the foregoing description, but embraces all such alterations, modifications and variations in accordance with the spirit and scope of the appended claims.
Claims (7)
1. A software method of operation of a radio data base station having a busy control mechanism comprising the steps of:
detecting a beginning portion of a packet having a signal strength;
setting a received signal strength indicator (RSSI) based on the signal strength of the beginning portion of the packet;
determining whether the RSSI of the beginning portion of the packet is greater than a predetermined threshold value, if the RSSI of the beginning portion of the packet is less than the predetermined threshold value, looking for a start of another packet; and if the RSSI of the beginning portion of the packet is greater than the predetermined threshold value, setting a busy bit and transmitting a busy signal.
detecting a beginning portion of a packet having a signal strength;
setting a received signal strength indicator (RSSI) based on the signal strength of the beginning portion of the packet;
determining whether the RSSI of the beginning portion of the packet is greater than a predetermined threshold value, if the RSSI of the beginning portion of the packet is less than the predetermined threshold value, looking for a start of another packet; and if the RSSI of the beginning portion of the packet is greater than the predetermined threshold value, setting a busy bit and transmitting a busy signal.
2 . A software method of operation of a radio data base station having a busy control mechanism comprising the steps of:
detecting a beginning portion of a packet having a signal strength;
setting a busy bit upon detection of the beginning portion of the packet;
transmitting a busy signal;
setting a received signal strength indicator (RSSI) based on the signal strength of the beginning portion of the packet;
determining whether the RSSI of the beginning portion of the packet is greater than a predetermined threshold value, if the RSSI of the beginning portion of the packet is less than the predetermined threshold value. clearing the busy signal and looking for a start of another uplink packet; and if the RSSI of the beginning portion of the packet is greater than the predetermined threshold value, continuing to transmit the busy signal.
detecting a beginning portion of a packet having a signal strength;
setting a busy bit upon detection of the beginning portion of the packet;
transmitting a busy signal;
setting a received signal strength indicator (RSSI) based on the signal strength of the beginning portion of the packet;
determining whether the RSSI of the beginning portion of the packet is greater than a predetermined threshold value, if the RSSI of the beginning portion of the packet is less than the predetermined threshold value. clearing the busy signal and looking for a start of another uplink packet; and if the RSSI of the beginning portion of the packet is greater than the predetermined threshold value, continuing to transmit the busy signal.
3. A software method of operation of a radio data base station having a busy control mechanism comprising the steps of:
detecting a beginning portion of a packet;
based on the step of detecting the beginning portion of the packet, setting a busy bit;
based on the step of setting the busy bit, transmitting a busy signal;
decoding a station identifier signal from the packet;
comparing the station identifier signal with a predetermined station identification for the radio data base station;
clearing the busy signal if the station identifier signal does not match the predetermined station identification of the radio data base station; and continuing to transmit the busy signal if the station identifier signal does match the predetermined station identification of the radio data base station.
detecting a beginning portion of a packet;
based on the step of detecting the beginning portion of the packet, setting a busy bit;
based on the step of setting the busy bit, transmitting a busy signal;
decoding a station identifier signal from the packet;
comparing the station identifier signal with a predetermined station identification for the radio data base station;
clearing the busy signal if the station identifier signal does not match the predetermined station identification of the radio data base station; and continuing to transmit the busy signal if the station identifier signal does match the predetermined station identification of the radio data base station.
4. The method of claim 3 further comprising, based on the step of continuing to transmit the busy signal, the steps of:
receiving the packet in its entirety; and clearing the busy signal.
receiving the packet in its entirety; and clearing the busy signal.
5. A software method of operation of a radio data base station having a busy control mechanism comprising the steps of:
detecting a beginning portion of a packet;
setting a busy bit;
transmitting a busy signal;
determining whether a beginning portion of the packet has a received signal strength indicator (RSSI) greater than a predetermined threshold value;
if the RSSI of the beginning portion of the packet is less than the predetermined threshold value, clearing the busy signal;
if the RSSI of the beginning portion of the packet is greater than the predetermined threshold value, determining whether a frame synchronization signal of the packet is detected before the frame synchronization signal times out;
if the frame synchronization signal is not detected before the frame synchronization signal times out, clearing the busy signal;
if the frame synchronization signal is detected before the frame synchronization signal times out, determining whether a station identifier signal of the packet is identical to a predetermined station identification at the radio data base station;
if the station identifier signal is not identical to a predetermined station identification at the radio data base station, clearing the busy signal;
if the station identifier signal is identical to a predetermined station identification at the radio data base station, determining whether a packet header is received correctly;
if the packet header is not received correctly, clearing the busy signal after one of a time-out and a determination that the RSSI of the packet has dropped below a threshold; and if the packet header is received correctly, receiving the packet in its entiretyand subsequently clearing the busy signal.
detecting a beginning portion of a packet;
setting a busy bit;
transmitting a busy signal;
determining whether a beginning portion of the packet has a received signal strength indicator (RSSI) greater than a predetermined threshold value;
if the RSSI of the beginning portion of the packet is less than the predetermined threshold value, clearing the busy signal;
if the RSSI of the beginning portion of the packet is greater than the predetermined threshold value, determining whether a frame synchronization signal of the packet is detected before the frame synchronization signal times out;
if the frame synchronization signal is not detected before the frame synchronization signal times out, clearing the busy signal;
if the frame synchronization signal is detected before the frame synchronization signal times out, determining whether a station identifier signal of the packet is identical to a predetermined station identification at the radio data base station;
if the station identifier signal is not identical to a predetermined station identification at the radio data base station, clearing the busy signal;
if the station identifier signal is identical to a predetermined station identification at the radio data base station, determining whether a packet header is received correctly;
if the packet header is not received correctly, clearing the busy signal after one of a time-out and a determination that the RSSI of the packet has dropped below a threshold; and if the packet header is received correctly, receiving the packet in its entiretyand subsequently clearing the busy signal.
6. A system of a radio data base station comprising:
a transceiver;
a busy signal generator coupled to the transceiver;
a station identifier comparator, having a predetermined station identification, coupled to the busy signal generator and coupled to the transceiver; and a signal detector coupled to the busy signal generator and coupled to the transceiver.
a transceiver;
a busy signal generator coupled to the transceiver;
a station identifier comparator, having a predetermined station identification, coupled to the busy signal generator and coupled to the transceiver; and a signal detector coupled to the busy signal generator and coupled to the transceiver.
7. A system of a radio data base station comprising:
a transceiver;
a signal output of the transceiver;
a signal strength memory unit having a first input coupled to a predetermined threshold value, a second input coupled to the signal output of the transceiver and an output coupled to a busy signal generator; and a signal detector coupled to the busy signal generator and coupled to the transceiver.
a transceiver;
a signal output of the transceiver;
a signal strength memory unit having a first input coupled to a predetermined threshold value, a second input coupled to the signal output of the transceiver and an output coupled to a busy signal generator; and a signal detector coupled to the busy signal generator and coupled to the transceiver.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US84676897A | 1997-04-30 | 1997-04-30 | |
| US08/846,768 | 1997-04-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2235231A1 true CA2235231A1 (en) | 1998-10-30 |
Family
ID=25298894
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002235231A Abandoned CA2235231A1 (en) | 1997-04-30 | 1998-04-17 | System and software method of operation of a radio data base station |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH1155178A (en) |
| CA (1) | CA2235231A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6191955B2 (en) * | 2013-09-17 | 2017-09-06 | Ｎｅｃプラットフォームズ株式会社 | Mobile communication system, mobile communication method, control device, and control program |
| CN108696927A (en) * | 2018-05-26 | 2018-10-23 | 四川省大见通信技术有限公司 | Digital junction equipment and the method for wireless network non-blind area covering and reducing power consumption |
-
1998
- 1998-04-17 CA CA002235231A patent/CA2235231A1/en not_active Abandoned
- 1998-04-23 JP JP10131415A patent/JPH1155178A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1155178A (en) | 1999-02-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7620063B2 (en) | Method for clear channel assessment optimization in a wireless local area network | |
| US7986946B2 (en) | Evaluation of random access preamble codes | |
| US6487420B1 (en) | Adaptive rach power determination for mobile telecommunications user equipment unit | |
| US7155247B2 (en) | Wireless communication network with automatic threshold adjustment | |
| US6631123B1 (en) | Method of improving user access performance by adjusting power of user probe signal | |
| KR100667610B1 (en) | Communication network with improved access protocol | |
| EP1434389A2 (en) | Communication apparatus in radio network, transmission control method, threshold value control method, and radio network system | |
| CA2235231A1 (en) | System and software method of operation of a radio data base station | |
| EP0522885B1 (en) | Method and arrangement of detecting control channel in mobile communications system | |
| JPH07297761A (en) | Hopping channel selection method for frequency hopping radio communication system | |
| US6947735B2 (en) | Method for avoiding interferences in cellular CDMA radio networks caused by defective mobile stations | |
| US5708964A (en) | Paging satelite line receiver having automatic signal acquisition | |
| US6456835B1 (en) | Arbitration method for high power transmissions in a code division multiple access system | |
| US6711405B2 (en) | Communication system | |
| JP2939112B2 (en) | Frequency hopping system Spread spectrum wireless communication system | |
| KR20190048871A (en) | System and method for monitoring spurious |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |