U.S. patent application number 10/750476 was filed with the patent office on 2005-06-30 for method and apparatus for reducing data collisions in a frequency hopping communication system.
Invention is credited to Black, Greg R., Kurby, Christopher N., Stewart, Kenneth A..
Application Number | 20050141596 10/750476 |
Document ID | / |
Family ID | 34701204 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050141596 |
Kind Code |
A1 |
Black, Greg R. ; et
al. |
June 30, 2005 |
Method and apparatus for reducing data collisions in a frequency
hopping communication system
Abstract
A method in a transmitter for data collision avoidance in an
uncoordinated frequency hopping communication system is disclosed.
The base station (104) first determines (304) that a first data set
to be sent to a first device (105) and a second data set to be sent
to a second device (107) are scheduled to be transmitted
simultaneously on a first frequency of a frequency hop-set. The
device then transmits (310) the first data set on the first
frequency of the frequency hop-set. The base station delays (312)
transmission of the second data set, and finally transmits (316)
the second data set on a second frequency of a frequency
hop-set.
Inventors: |
Black, Greg R.; (Vernon
Hills, IL) ; Kurby, Christopher N.; (Elmhurst,
IL) ; Stewart, Kenneth A.; (Grayslake, IL) |
Correspondence
Address: |
MOTOROLA INC
600 NORTH US HIGHWAY 45
ROOM AS437
LIBERTYVILLE
IL
60048-5343
US
|
Family ID: |
34701204 |
Appl. No.: |
10/750476 |
Filed: |
December 31, 2003 |
Current U.S.
Class: |
375/133 ;
375/E1.036 |
Current CPC
Class: |
H04B 2001/7154 20130101;
H04B 1/715 20130101; H04W 72/12 20130101; H04W 28/10 20130101; H04W
88/08 20130101 |
Class at
Publication: |
375/133 |
International
Class: |
H04B 001/713 |
Claims
What is claimed is:
1. A method in a transmitter for data collision avoidance in an
uncoordinated frequency hopping communication system comprising:
determining that a first data set to be sent to a first device and
a second data set to be sent to a second device are scheduled to be
transmitted simultaneously on a first frequency; transmitting one
of the first data set and the second data set on the first
frequency; delaying transmission of an other of the first data set
and the second data set; and transmitting the other of the first
data set and the second data set on a second frequency.
2. The method according to claim 1, delaying transmission of the
second data set temporally to the next scheduled transmission
time.
3. The method according to claim 2, wherein the first frequency is
one of a plurality of frequencies of a first frequency hopping
pattern.
4. The method according to claim 2, wherein the second frequency is
one of a plurality of frequencies of a second frequency hopping
pattern.
5. The method according to claim 3, wherein the second frequency is
one of a plurality of frequencies of a second frequency hopping
pattern.
6. The method according to claim 5, further comprising transmitting
the second data set on a frequency which is sequentially next in a
frequency hop-set.
7. The method according to claim 3, further comprising, prior to,
transmitting one of the first data set and the second data set,
randomly selecting either the first data set or the second data set
to be transmitted first.
8. The method according to claim 7, wherein transmitting one of the
first data set and the second data set further comprises
transmitting the randomly selected data set of the first or second
data set during a scheduled transmission frame and on a scheduled
transmission frequency, and wherein delaying further comprises
delaying the data set of the first or second data set not randomly
selected to the next scheduled transmission frame.
9. The method according to claim 8, wherein transmitting the other
of the first data set and the second data set further comprises
transmitting the data set not randomly selected at the next
scheduled frame and on the next scheduled transmission
frequency.
10. The method according to claim 9, further comprising assigning a
first sub-channel code to the first device.
11. The method according to claim 10, further comprising inserting
the sub-channel code, that correlates to the first sub-channel code
assigned to the first device, into the first data set to be
transmitted.
12. The method according to claim 11, further comprising assigning
a second sub-channel code to the second device.
13. The method according to claim 12, further comprising inserting
the second sub-channel code, that correlates to the second
sub-channel code assigned to the second device into the second data
set to be transmitted to the second device.
14. A method in a transmitter for data collision avoidance in an
uncoordinated frequency hopping communication system comprising:
determining that a first data set to be sent to a first device and
a second data set to be sent to a second device are scheduled to be
transmitted simultaneously on a first frequency; transmitting the
first data set on the first frequency; and discarding the second
data set.
15. A method in a transmitter for data collision avoidance in an
uncoordinated frequency hopping communication system comprising:
receiving, from a base station, a channel frequency set and hopping
patterns of all wireless devices in the frequency hopping
communication system using a hop-set; determining when a channel
collision will occur using the received channel frequency set and
the hopping patterns; transmitting a first data set on the first
frequency; and delaying transmission of a second data set.
16. A method in a wireless communication device to eliminate data
collisions in an uncoordinated frequency hopping communication
system comprising: receiving a first data set on the first
frequency hopping frequency; determining that the first data set
was not intended to be received by the device; delaying
transmission of a second data set; and transmitting the second data
set on a second frequency of a frequency hopping pattern.
17. The method according to claim 16, wherein the step of
determining that the first data set was not intended to be received
by the device comprises: comparing a first sub-channel code in said
first data set to a sub-channel code assigned to the wireless
communication device. determining that the first sub-channel code
in said first data set does not match the sub-channel code assigned
to the wireless communication device.
18. The method according to claim 17, wherein the second data set
is transmitted on a second frequency which is sequentially next in
a frequency hopping pattern.
19. A method in a wireless communication device to eliminate data
collisions wherein transmissions are made in an uncoordinated
frequency hopping scheme such that the downlink channels and uplink
channels are assigned in pairs, and wherein the uplink channel
assignment follows the downlink assignment and uplink channel
collisions occur following downlink channel collisions, said method
comprising: determining that a downlink channel collision has
occurred; refraining from transmitting an uplink data set during
the scheduled uplink period; and transmitting the uplink data set
on the next scheduled uplink period thereby avoiding an uplink
channel collision.
20. The method according to claim 19, wherein determining that a
downlink channel collision has occurred further comprises
determining that a downlink data set received by the device was not
intended to be received by the device.
21. The method according to claim 20, wherein determining that a
downlink channel collision has occurred further comprises
determining that a sub-channel code included in the downlink data
set received by the device does not match an assigned sub-channel
code.
22. The method according to claim 21, wherein determining that a
downlink channel collision has occurred further comprises
determining that a priority code does not match an assigned
priority code.
23. A method in a transmitter for data collision avoidance in a
frequency hopping communication system comprising: determining that
a first data set to be sent to a first device and a second data set
to be sent to a second device are scheduled to be transmitted
simultaneously on a first uncoordinated frequency hopping
frequency; transmitting the first data set on the first frequency
hopping frequency; delaying transmission of the second data set;
transmitting the second data set on a second frequency hopping
frequency; transmitting a third data set to a third device on a
first coordinated frequency hopping frequency.
24. A base station in a wireless communication system comprising: a
message reception module, wherein messages received by the message
reception module are to be transmitted to one of a plurality of
communication devices; a frequency hop pattern generation module; a
channel collision detection module that detects when received
messages are scheduled to be transmitted on the same frequency at
the same time; a message scheduling module; and a message
transmitter.
25. A mobile station adapted to communicate in a frequency hopping
wireless communication system comprising: a receiver module,
wherein messages are received on a frequency of an uncoordinated
frequency hopping hop-set; a channel collision detection module
that detects when received messages are not intended to be received
by the mobile station; a transmission scheduling module; and a
transmitter.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to wireless
communications, and more particularly to eliminating data
collisions in a frequency hopping communication system.
BACKGROUND OF THE INVENTION
[0002] Wireless communication devices generally operate in either
licensed RF bands or an unlicensed RF bands. Radiotelephone service
providers generally acquire licenses to operate a wireless
communication system in one or more of a plurality of licensed RF
bands. These systems employ multiple methods to allow multiple
access by multiple mobile stations on a common band of frequency
channels. One such access technique, frequency division multiple
access (FDMA), allows multiple access by assigning the mobile
stations to different frequency channels within the RF band. Some
of these systems employ frequency hopping, wherein data is
transmitted to and from the intended mobile station while
periodically changing the frequency channel. The periodic channel
frequency hopping occurs on a regular time interval known as a
frame. Coordinated frequency hopping systems use predetermined
hopping patterns, or hop-sets, wherein the hop-sets are coordinated
between all mobile stations to ensure that the signals to and from
two or more mobile stations do not occur simultaneously on the same
frequency channel. Uncoordinated frequency hopping does not
coordinate the hop-set between mobile stations resulting in the
periodic occurrence of simultaneous signal transmission on the same
frequency. Such simultaneous transmissions are referred to as
channel collisions. Data reception errors occurring during a
channel collision are referred to as data collisions. Uncoordinated
frequency hopping within this type of system is generally not used
as the channel collisions and resultant data collisions will occur.
The FCC has prohibited coordinated frequency hopping within the
Industrial Scientific and Medical (ISM) bands in order to avoid
spectrum aggregation by a single type of service.
[0003] Systems such as Bluetooth and 802.11 wireless communication
systems, for example operate within the ISM bands. To avoid data
collisions these systems may monitor the band and choose to operate
only in unoccupied sub-bands. These systems may also change
sub-bands as the result of the detection of interferer signal
strength or the detection of signaling errors indicative of a
channel collision with another transmitting station. However
channel collisions still occur as devices must sense the
interference caused by a channel collision in order to change the
frequency sub-band.
[0004] Therefore, in order for a GSM system to be compliant with
FCC regulations a change to the hopping channel assignment scheme
is needed such that the hopping channel assignments are
uncoordinated. Therefore, what is needed is a method for the
elimination of data collision errors caused by frequency hopping
channel collisions in an uncoordinated frequency hopping
system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The various aspects, features and advantages of the present
invention will become more fully apparent to those having ordinary
skill in the art upon careful consideration of the following
Detailed Description of the Drawings with the accompanying drawings
described below.
[0006] FIG. 1 is an exemplary diagram of a communication
system;
[0007] FIG. 2 is an exemplary block diagram of a wireless
communication device;
[0008] FIG. 3 is an exemplary flow diagram of a data transmission
method;
[0009] FIG. 4 is an exemplary flow diagram of a data reception
method;
[0010] FIG. 5 is an exemplary flow diagram of a data reception
method; and
[0011] FIG. 6 is an exemplary flow diagram of a data transmission
method.
DETAILED DESCRIPTION OF THE DRAWINGS
[0012] A method for the elimination of data collision errors in an
uncoordinated frequency hopping communication system is disclosed.
The method comprises determining that a first data set, which is to
be sent to a first device, and a second data set, which is to be
sent to a second device, is scheduled to be transmitted
simultaneously on a first frequency, i.e. a channel collision. The
data collision is avoided between the two data sets, by
transmitting the first data set on the first frequency hopping
frequency, while the second data set is delayed, also known as
muted. The first data set is thereby transmitted unambiguously and
data collisions are avoided in the first device. The final step is
transmitting the second data set on a second frequency hopping
frequency, sequentially next in the frequency hop pattern at the
next frame. The second data set is thereby transmitted
unambiguously with a delay of at least one frame. Thus the hopping
channels are uncoordinated, since the original uncoordinated
hopping sequences are unmodified except for the muting of the
transmission to the second device during the channel collision.
Data collisions are avoided in the second device during the
transmission of the first data set by a determination that the
second device is not the intended recipient, and suspension of data
reception until another frame.
[0013] Due to RF spectrum limitations, an increase in users and the
cost of RF spectrum licenses, wireless telecommunications service
providers can benefit from using unlicensed RF spectrum to
complement the licensed spectrum portion of their systems. Although
the spectrum is unlicensed, use-requirements may still apply. One
example is the use of unlicensed RF bands to augment GSM
radiotelephone services. The GSM system can use coordinated
frequency hopping in which each mobile station in a cell uses the
same set of channel frequencies and hopping pattern, and a unique
time offset of the hopping pattern determined by the mobile
allocation index offset (MAIO). In this way the system can
accommodate one communication signal for each hopping channel
without the occurrence of channel collisions within the same
cell.
[0014] FIG. 1 is an exemplary diagram of a wireless communication
system 100 according to the present invention. The system 100
includes a base station controller (BSC) 102, also known as a radio
network controller (RNC) 102 in some systems, at least one base
station 104, and a first wireless device 105, also known as a
mobile station (MS) 105, and a second wireless device 107. The BSC
102 and the base stations 104 form the radio access network (RAN)
106 portion of the system which communicates with the wireless
devices. A core network, which is coupled to the RAN, includes a
mobile switching center (MSC) and may include a serving GPRS
support node (SGSN). The core network (CN) 108 portion of the
system, illustrated in FIG. 1, includes a first MSC 110 and a first
SGSN 112 for a first service provider. The system 100 may also
include a second MSC 114 and a second SGSN 116 for a second service
provider. In the exemplary embodiment shown in FIG. 1, only two
core networks are illustrated but it is understood by one skilled
in the art that a plurality of core networks may be coupled to a
RAN.
[0015] The base station 104 receives messages from the BSC 102 and
transmits the messages to the intended wireless devices under an
uncoordinated frequency hopping scheme. Communications between the
base station 104 and the first wireless device 105 share a first
uncoordinated hop-set while the base station 104 and the second
wireless device 107 share a second uncoordinated hop-set. There is
no coordination between the first uncoordinated hop-set and the
second uncoordinated hop-set, however these hop-sets may comprise
common frequency channels such that frequency channel collisions
may occur. The wireless devices may be mobile stations or other
user equipment that communicate with a serving node, such as the
exemplary base station 104 of the communication system 100 in
FIG.1. Each wireless device however is coordinated with the base
station 104 to necessarily form the communication link between the
two. Information represented in the data sets which are to be
transmitted to the wireless devices either originate at the BSC
102, or are received at the BSC 102 from the core network 108 to be
relayed to the intended wireless device. The information can be
either packet-switched data or circuit-switched data and the
information may be voice information or data information.
[0016] Turning to FIG. 2, a block diagram of a wireless
communication device 200 in accordance with one embodiment of the
invention is shown. This embodiment can be a cellular
radiotelephone incorporating the present invention. However, it is
to be understood that the present invention is not limited to this
embodiment and may be utilized by other wireless communication
devices such as paging devices, personal digital assistants,
portable computing devices, and the like, having wireless
communication capabilities. In this embodiment a frame generator
202 and a microprocessor 204, combine to generate the necessary
communication protocol for operating in a wireless communication
system. Microprocessor 204 uses memory 206 comprising RAM 207, s
EEPROM 208, and ROM 209, which can be consolidated in one package
210, to execute the steps necessary to generate the protocol and to
perform other functions for the wireless communication device, such
as writing to a display 212, accepting information from a keypad
214, or controlling a frequency synthesizer 226 to attune the
device to the appropriate frequency in a frequency hopping pattern.
The memory may also include a SIM card 232. In situations where the
wireless device is used for voice transmissions, the frame
generator 202 processes audio transformed by audio circuitry 218
from a microphone 220 and to a speaker 222.
[0017] FIG. 2 also shows at least one transceiver 227 comprising
receiver circuitry 228, that is capable of receiving RF signals
from at least one bandwidth and optionally more bandwidths. The
receiver 228 may optionally comprise a first receiver and a second
receiver, or one receiver capable of receiving in two or more
bandwidths. The receiver 228, depending on the mode of operation,
may be tuned to receive PLMRS, AMPS, GSM, EGPRS, CDMA, UMTS, WCDMA,
Bluetooth, or WLAN, such as 802.11 communication signals for
example. The transceiver 227 includes at least one transmitter 234.
The at least one transmitter 234 may be capable of transmitting to
one device or base station in one frequency band and potentially on
multiple frequency bands. As with the receiver 228, dual
transmitters 234 may optionally be employed where one transmitter
is for the transmission to a proximate device or direct link
establishment to WLAN's and the other transmitter is for
transmission to the base station 108.
[0018] The wireless communication device 200, which can be adapted
to communicate in a frequency hopping wireless communication, may
also comprise a channel collision detection module 224 that detects
when received messages are not intended to be received by the
mobile station 200 and a transmission scheduling module 225 both
coupled to the microprocessor 204.
[0019] A base station 104 of the wireless communication system can
include a transmitter 120 and a receiver 122 for communicating with
a plurality of wireless communication devices. The base station 104
can also include a message reception module 124, that receives
messages from the core network which are to be transmitted to one
of a plurality of wireless communication devices. The base station
may also include a frequency hop pattern generation module 126. The
frequency hop pattern generation module 126 determines the
frequency hop-set pattern for each device of the plurality of
devices. The frequency hop-set patterns are uncoordinated from
device to device. The base station 104 can also include a channel
collision detection module 128 that detects when received messages
are scheduled to be transmitted on the same frequency at the same
time and a message scheduling module that reschedules or delays
transmission of a data set that was determined to collide with
another data set.
[0020] FIG. 3 shows an exemplary flow diagram 300 illustrating how
a first data set is received 302 at the base station 104 for
transmission to the intended mobile station. The intended mobile
station can be the first wireless device 105 in this exemplary
embodiment. In step 302, the first data set is received at a first
time on a first frequency of a first uncoordinated frequency
hop-set. Similarly, a second data set is also received at the base
station 104 for transmission to the intended mobile station, the
second mobile station 107 in this exemplary embodiment. The first
data set and the second data set do not necessarily arrive at the
base station 104 at the same time. It is envisioned that they can
in fact be received independently. The second data set can be also
scheduled to be sent at the first time on the first frequency of a
second uncoordinated frequency hop-set. The base station 104 can
determine in step 304 that a data collision will occur as both the
first and the second data set are scheduled to be transmitted on
the same frequency at the same time. In step 308, the base station
104 can determine which data set to send first or at all. In step
310, the first data set is then transmitted to the first wireless
device 105 in this exemplary embodiment. This provides for an
unambiguous transmission to the first wireless device 105. In step
312, the second data set is delayed, or muted and not transmitted
at the scheduled time or on the scheduled frequency. If the second
data set is to be delayed, in step 314, the second data set may be
delayed one cycle in the frequency hop-set. In step 316, the second
data set can then be sent to the second device at the delayed time
on the next frequency. If in step 304 the base station 104
determines that a collision will not occur, the base station 104
transmits, in step 306, both data sets as scheduled in accordance
with each respective hop-set. The second data set may also be
discarded instead of transmitted.
[0021] Although two data sets are used for exemplary purposes
throughout this disclosure, it is envisioned that a plurality of
data sets may be scheduled to be transmitted simultaneously and on
the same frequency as the individual frequency hop-sets associated
with each device are uncoordinated between the devices. As the
number of wireless devices communicating in the communication
system increases, the potential for data collisions also increases.
Therefore the base station 104 must check the scheduling of all
messages to be transmitted, in accordance with the above method, to
avoid collisions.
[0022] FIG. 4 is an exemplary flowchart 400 outlining the operation
of a wireless device according to an exemplary embodiment. For
example, the second wireless device 107 can be the intended
recipient of the second data set from the base station 104. As the
base station 104 has delayed 312 the transmission of the second
data set, the second device 107 can receive 402 the first data set
during the scheduled time the second device 107 is supposed to
receive the second data set. If, step 404, the second wireless
device 107 determines the first data set is actually intended for
the second wireless device 107, in step 406, the second wireless
device 107 processes the data. If in step 404, the second wireless
device 107 determines that it is not the intended recipient for the
data transmitted by the base station, i.e. the first data set, the
first data set is discarded 408 or reception is suspended.
[0023] Continuing with reference to FIG. 4, the second device 107
can then tune 410 to the next scheduled frequency in the hop
pattern allowing that device to receive 412 the second data set at
the next frequency, at the next scheduled frame. The next frequency
in the hopping pattern is the next scheduled frequency in the
hop-set, such that the hopping pattern resumes at the next
scheduled frame. In this way the two hopping patterns, a first
hopping pattern for the first device 105 and a second hopping
pattern for the second device 107, are uncoordinated hopping
patterns since the hopping patterns are unaltered after the
occurrence of a channel collision.
[0024] The base station 104 should determine which data set should
be transmitted after determining 304 that a channel collision will
occur. In one exemplary embodiment, the base station 104 or the
base station controller 102 can send the data set received first in
time at the base station 104 or the base station controller 102. In
this exemplary embodiment, the data sets are processed on a first
in first out (FIFO) basis. In another exemplary embodiment, the
data set to be sent first is randomly selected. If multiple data
sets are scheduled to collide, all except one data set would have
to be rescheduled. It should be noted that multiple transmissions
can occur at the same time. However, multiple transmissions can not
occur at the same time on the same frequency without causing data
collisions and resultant data errors in the wireless device
receivers. In another embodiment, priority is given according to
the radiated power at the base station 104. A higher priority is
assigned for example to a device that requires higher radiated
power at the base station 104. It may also be the case that the
higher priority is assigned to a device that requires lower
radiated power at the base station 104. In yet another embodiment,
priority is given according to the needs of the wireless device,
whereby voice data may be given higher priority than other types of
data, for example. It is understood by one skilled in the art that
there are a plurality of methods for determining which data set to
send and in what order, and the disclosure is not limited to those
exemplary embodiments listed herein.
[0025] FIG. 5 is an exemplary flowchart outlining a method 500 for
determining that the data is not intended to be received by either
of the exemplary first wireless device 105 or the second wireless
device 107. For example, this process may be used in step 404 of
the flowchart 400. In this embodiment, a unique sub-channel code
can be assigned 502 to each wireless device using the hop-set. The
unique sub-channel code can be inserted 504 into each transmission.
In this exemplary embodiment, the unique sub-channel code can be
included in a control field in the received data set. The unique
sub-channel code allows each device to determine which data set,
the first data set or the second data set in the exemplary
embodiment, is intended to be received by the respective device.
The wireless device 105, 107 can then decode 506 the control field
upon reception of the data set and determine 508 if the unique
sub-channel code in the received data set matches the unique
sub-channel code assigned to the wireless device by the base
station 104. If the unique sub-channel code matches 510, then
device processes 512 the data. If the unique sub-channel code does
not match 514, the data set is discarded 516.
[0026] For example, in an exemplary GSM system, a GSM traffic
channel (TCH) might be modified to include a temporary mobile
station identity code (TMSIC), which is the unique sub-channel code
having a unique value for every wireless device receiving a data
set, i.e. data transmissions, from the base station on a particular
hop-set of hopping frequencies channels. Upon decoding the TMSIC
the second mobile station will determine that the received TMSIC is
different that its TMSIC assignment and discard the received data
or suspend reception.
[0027] Referring to FIG. 6, in another exemplary embodiment
flowchart 600, the wireless devices, such as the first and second
wireless device 105, 107, receive 602, from the base station 104, a
unique priority code which is assigned to each wireless device
using the hop-set of frequency hopping channels. The wireless
device, 105, 107 then receive 604 from the base station 104 the
channel frequencies and hopping patterns of all wireless devices
using a hop-set. The received frequencies and hopping patterns are
used by the wireless devices 105, 107 to predict or determine when
channel collisions will occur. For example when the first wireless
device 105 detects 606 a channel collision, the first device 105
can use a predetermined rule set to determine 608 the intended
recipient of the information transmitted by the base station 104.
The predetermined rule set assures that only one recipient is
assigned during a channel collision.
[0028] In one exemplary embodiment of this approach, the first
wireless device 105 is assigned a device priority of "1", and a
device priority of "0" is assigned to all other wireless devices
using the hop-set. The first device 105 will receive 610 the first
message which has the higher priority code. The first device 105
will discard 612 any message with a "0" priority. If there will not
be a channel collision, the message is received and processed 614.
In this embodiment, multiple devices can be given the priority of
"1" and when a channel collision is detected, the rule set
determines which device with the "1" priority to receive the data
set, with all other data set transmissions being delayed until the
next scheduled frame. In another exemplary embodiment the device
priority might automatically change according to predetermined
rules after each channel collision, such that the mobile stations
alternate using the channel during channel collisions. Upon
determining that a channel collision will occur and that the
transmitted data set is intended for a different wireless device,
the second device suspends reception. The priority of "1" and "0"
are exemplary values and the values may be integrated over a range
of values for example.
[0029] Complimentary to the mobile station operation, after the
base station detects that the channel collision will occur; the
base station must determine if the channel collision involves data
being sent to at least one device with a higher priority code. The
base station will determine if a first message has a priority code
higher than a second message. In this exemplary embodiment, only
the first wireless device with the priority of "1" will receive the
transmission of the first message when a channel collision occurs.
The base station will send the first message which has the higher
priority code and delay the message or messages with the lower
priority code.
[0030] In the above exemplary embodiments, the methods allow for
the avoidance of data collisions in the downlink transmissions from
base station to mobile station, i.e. wireless device. Analogous
techniques may be applied for avoiding data collisions on the
uplink transmissions, i.e. transmissions between mobile stations
and the base station. This applies to the situation in which the
uplink and down-link hop sets are uncoordinated. However it is
anticipated that coordination of up-link and down-link hop-sets
will be allowed. In the cases such where the downlink and uplink
channels are assigned in pairs, one exemplary embodiment provides a
method where the uplink channel assignment follows the downlink
assignment on the same frequency channels. In another exemplary
embodiment, such as in the GSM case, the uplink channel follows the
downlink channel with a fixed frequency offset. According to this
approach, whenever a downlink channel collision occurs there will
necessarily be a corresponding uplink collision. Thus, in this
exemplary embodiment, when a wireless device receives a downlink
data set during a channel collision as in accordance with one of
the approaches described above, it will then transmit its uplink
data set on the scheduled uplink transmission period, whereas if a
wireless device does not receive a data set during a channel
collision it will refrain from transmitting its data set on the
scheduled uplink period, and wait until the next scheduled uplink
period to transmit the data set on the next channel frequency in
the hop-set, thereby avoiding an uplink data collision.
[0031] While the present inventions and what is considered
presently to be the best modes thereof have been described in a
manner that establishes possession thereof by the inventors and
that enables those of ordinary skill in the art to make and use the
inventions, it will be understood and appreciated that there are
many equivalents to the exemplary embodiments disclosed herein and
that myriad modifications and variations may be made thereto
without departing from the scope and spirit of the inventions,
which are to be limited not by the exemplary embodiments but by the
appended claims.
* * * * *