U.S. patent application number 14/933713 was filed with the patent office on 2016-02-25 for method for resolving call collisions in a digital conventional direct mode.
The applicant listed for this patent is MOTOROLA SOLUTIONS, INC.. Invention is credited to DIPENDRA M. CHOWDHARY, SANJAYKUMAR S. KARPOOR, SATYANARAYAN R. PANPALIYA, BADARINATH PATIBANDLA, DAVID G. WIATROWSKI.
Application Number | 20160057782 14/933713 |
Document ID | / |
Family ID | 51487707 |
Filed Date | 2016-02-25 |
United States Patent
Application |
20160057782 |
Kind Code |
A1 |
PANPALIYA; SATYANARAYAN R. ;
et al. |
February 25, 2016 |
METHOD FOR RESOLVING CALL COLLISIONS IN A DIGITAL CONVENTIONAL
DIRECT MODE
Abstract
A process for resolving call collisions in a digital
conventional direct mode includes monitoring a direct mode
communication channel for transmissions from other direct mode
radios in the plurality of direct mode radios. In response to
detecting a new call request: identifying a last radio to transmit
on the direct mode channel, transmitting a new call request for
receipt by the last direct mode radio to transmit, monitoring the
direct mode channel for a response from the last radio to transmit,
and if a call grant granting the new call request is received from
the last radio to transmit, initiating the new direct mode call on
the direct mode communication channel. If the call grant is not
received, at least temporarily refraining from initiating the new
direct mode call.
Inventors: |
PANPALIYA; SATYANARAYAN R.;
(PALATINE, IL) ; CHOWDHARY; DIPENDRA M.; (HOFFMAN
ESTATES, IL) ; KARPOOR; SANJAYKUMAR S.; (BUFFALO
GROVE, IL) ; PATIBANDLA; BADARINATH; (SCHAUMBURG,
IL) ; WIATROWSKI; DAVID G.; (WOODSTOCK, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MOTOROLA SOLUTIONS, INC. |
Schaumburg |
IL |
US |
|
|
Family ID: |
51487707 |
Appl. No.: |
14/933713 |
Filed: |
November 5, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13793621 |
Mar 11, 2013 |
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14933713 |
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Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 72/1242 20130101;
H04W 76/14 20180201; H04W 74/0816 20130101; H04W 92/18 20130101;
H04W 76/18 20180201; H04W 72/14 20130101 |
International
Class: |
H04W 74/08 20060101
H04W074/08; H04W 72/14 20060101 H04W072/14; H04W 72/12 20060101
H04W072/12; H04W 76/02 20060101 H04W076/02 |
Claims
1. A method for resolving call collisions in a direct mode
communication system among a plurality of direct mode radios, the
method comprising, at a first direct mode radio out of the
plurality of direct mode radios: transmitting, on a direct mode
communication channel, one or more transmissions during a first
direct mode call to the other direct mode radios in the plurality
of direct mode radios, the transmissions including an identifier
identifying the first direct mode radio; after making the last
transmission of the first direct mode call, transitioning to an
arbitrating mode for the direct mode communication channel and
monitoring the direct mode communication channel for any new direct
mode call requests from other direct mode radios in the plurality
of direct mode radios.
2. The method of claim 1, further comprising: receiving, from a
second direct mode radio out of the plurality of direct mode
radios, a first new direct mode call request; monitoring the direct
mode communication channel for any additional new direct mode call
requests from other direct mode radios in the plurality of direct
mode radios; and responsive to determining that one of (i) no other
new direct mode call requests have been received and (ii) other new
direct mode call requests have been received but the first new
direct mode call request is entitled to priority over the other new
call requests; broadcasting a call grant granting the first new
direct mode call request of the second direct mode radio, the call
grant including an identifier identifying the second direct mode
radio; and receiving and playing back content received from the
second direct mode radio broadcast over the direct mode
communication channel during the first new direct mode call
generated by the acknowledgment.
3. The method of claim 2, further comprising determining that no
other direct mode call requests are received.
4. The method of claim 2, further comprising receiving other new
direct mode call requests, determining that other new direct mode
call requests have been received, and determining that the first
new direct mode call request is entitled to priority over the other
new call requests;
5. The method of claim 2, further comprising: responsive to
receiving and playing back content received from the second direct
mode radio, identifying the second direct mode radio as the last
one of the other direct mode radios to transmit on the direct mode
communication channel and storing an identity of the second direct
mode radio for use in arbitrating future new call requests.
6. The method of claim 2, wherein: the direct mode call request
comprises a voice header or preamble control signaling block (CSBK)
including a target device identifier field populated with a device
identifier associated with the first direct mode radio.
7. The method of claim 1, wherein: monitoring the direct mode
communication channel for transmissions from other direct mode
radios in the plurality of direct mode radios comprises monitoring
the direct mode communication channel for transmissions including a
particular system identifier with which the first direct mode radio
is also associated with and includes in its transmissions.
8. The method of claim 1, further comprising: responsive to one of
a received instruction to power-off or otherwise disable its
transceiver or an error condition indicative of an inability to
receive transmissions over the direct mode communications channel,
broadcasting an announcement indicating that the first direct mode
radio will no longer be available to arbitrate new call requests on
the direct mode channel.
9. The method of claim 1, wherein the plurality of direct mode
radios communicate in accordance with a European Telecommunications
Standard Institute-Digital Mobile Radio (ETSI-DMR) direct mode
protocol.
10. The method of claim 1, wherein the direct mode communication
system has no infrastructure equipment.
11. The method of claim 1, wherein direct mode is a mode of
operation where radios communicate directly with each other over a
single shared RF frequency without the use of any infrastructure
equipment.
12. The method of claim 1, wherein infrastructure equipment
comprises: base stations, repeaters, and any and all other external
network infrastructure equipment.
Description
FIELD OF THE DISCLOSURE
[0001] The present disclosure relates generally to wireless
communications and more particularly to direct mode call collision
avoidance in a digital conventional direct mode communications
system.
BACKGROUND
[0002] The European Telecommunications Standard Institute-Digital
Mobile Radio (ETSI-DMR) is a direct digital replacement for analog
Private Mobile Radio (PMR). DMR is a scalable system that can be
used in unlicensed mode (in a 446.1 to 446.2 MHz band), and in
licensed mode, subject to national frequency planning ETSI
standards or specifications referred to herein may be obtained by
contacting ETSI at ETSI Secretariat, 650, route des Lucioles, 06921
Sophia-Antipolis Cedex, FRANCE.
[0003] DMR provides improved range, higher data rates, more
efficient use of spectrum, and improved battery life over prior
direct mode protocols. Features supported include fast call set-up,
calls to groups and individuals, and short data and packet data
calls. Supported communications modes include individual calls,
group calls, and broadcast calls provided via a direct
communication mode among the radios operating within the network.
Other direct mode functions such as emergency calls, priority
calls, full duplex communications, short data messages and Internet
Protocol (IP)-packet data transmissions are also supported.
[0004] Direct mode, more generally, is a mode of operation where
radios may communicate within a network without the assistance of
one or more infrastructure equipment (e.g., base stations or
repeaters). A radio, as used herein, can be mobile and/or fixed end
equipment that is used to obtain direct mode communications
services. Direct mode operation is contrasted with a conventional
repeater mode, which is a mode of operation where radios
communicate with one another through infrastructure equipment such
as a repeater or base station. Direct mode, therefore, can provide
a more efficient and less costly communication system operation
than repeater mode operation.
[0005] The ETSI-DMR standard provides for 12.5 Kilohertz (KHz)
operation in direct mode (systems that exclusively communicate
without a repeater). The 12.5 KHz operation refers to 12.5 KHz
spectral efficiency in which there are two communication paths per
12.5 KHz of radio frequency (RF) spectrum. The 12.5 direct mode
utilizes 27.5 millisecond (msec) pulsed (every 60 msec) radio
transmissions on each of the logical channels. In the 12.5 direct
mode of operation, radios transmit asynchronously and radios within
range of the transmission synchronize themselves to that
transmission for the purposes of receiving the transmission, but
any transmissions in response to the first transmission are
transmitted asynchronously.
[0006] Other direct mode protocols, perhaps consistent with the
Project 25 (P25) standard defined by the Association of Public
Safety Communications Officials International (APCO) and
standardized under the Telecommunications Industry Association
(TIA), or with the terrestrial trunked radio (TETRA) standard also
defined by the ETSI, may operate in a similar manner and may be
used in addition to or in place of the DMR protocol. Communications
in accordance with any one or more of these direct mode
communication standards, or other standards, may take place over
physical channels in accordance with one or more of a TDMA (time
division multiple access), FDMA (frequency divisional multiple
access), or CDMA (code division multiple access) protocol.
[0007] In prior analog direct mode communications systems, two or
more simultaneous direct mode transmissions can be mixed at the RF
level and the recipient thus able to hear the mixture of all the
conversations. However, in a digital conventional direct mode
consistent with any one of the foregoing mentioned standards, two
or more sources transmitting simultaneously would corrupt both of
the digital transmissions and, as a result, the recipients would
not hear any conversation. Even worse, the simultaneously
transmitting digital radio users would not be aware of the
corrupted transmission and may (incorrectly) assume that the
transmissions reached their respective targeted group of recipient
digital direct mode radios. This issue is further exacerbated in
digital direct mode group calls, where the number of digital direct
mode radios in the group (e.g., more than five) increases the odds
that simultaneous transmissions would conflict.
[0008] Accordingly, there is a need to provide an improved call
collision arbitration process and apparatus in digital conventional
direct mode communication systems in order to improve the
robustness of the communications systems and ensure that digital
transmissions are not corrupted by multiple simultaneous direct
mode digital transmissions.
BRIEF DESCRIPTION OF THE FIGURES
[0009] The accompanying figures, where like reference numerals
refer to identical or functionally similar elements throughout the
separate views, together with the detailed description below, are
incorporated in and form part of the specification, and serve to
further illustrate embodiments of concepts that include the claimed
invention, and explain various principles and advantages of those
embodiments.
[0010] FIG. 1 is a block diagram of an illustrative digital
conventional direct mode wireless communications system operating
in accordance with an embodiment.
[0011] FIG. 2 is a timing diagram illustrating one example of a
call transmission in a digital conventional direct mode wireless
communication system in accordance with an embodiment.
[0012] FIG. 3 is a block diagram of a direct mode wireless radio
operable in the digital conventional direct mode wireless
communications system of FIG. 1 in accordance with some
embodiments.
[0013] FIG. 4 is a flowchart illustrating a process, executable at
an initiating direct mode radio for resolving call collisions in a
digital conventional direct mode wireless communication system in
accordance with some embodiments.
[0014] FIG. 5 is a flowchart illustrating a process, executable at
an arbitrating/last transmitting direct mode radio for resolving
call collisions in a digital conventional direct mode wireless
communication system in accordance with some embodiments.
[0015] Skilled artisans will appreciate that elements in the
figures are illustrated for simplicity and clarity and have not
necessarily been drawn to scale. For example, the dimensions of
some of the elements in the figures may be exaggerated relative to
other elements to help to improve understanding of embodiments of
the present invention.
[0016] The apparatus and method components have been represented
where appropriate by conventional symbols in the drawings, showing
only those specific details that are pertinent to understanding the
embodiments of the present invention so as not to obscure the
disclosure with details that will be readily apparent to those of
ordinary skill in the art having the benefit of the description
herein.
DETAILED DESCRIPTION
[0017] In light of the foregoing, it would be advantageous to
provide for a method and device that monitors direct mode
communications, detects new call requests, identifies a last radio
to transmit, transmits a new call request to the last radio to
transmit, monitors for a response from the last one of the other
direct mode radios to transmit on the direct mode communication
channel, and acts accordingly based on whether or not an
acknowledgement of the call request is received from the last one
of the direct mode radios to transmit. Similarly, it would be
advantageous to provide for a method and device for a
last-to-transmit radio to arbitrate and grant or not grant
subsequent new call requests in a direct mode communication
channel.
[0018] In one embodiment, a process for resolving call collisions
in a digital conventional direct mode includes monitoring a direct
mode communication channel for transmissions from other direct mode
radios in the plurality of direct mode radios. In response to
detecting a new call request: identifying a last radio to transmit
on the direct mode channel, transmitting a new call request for
receipt by the last direct mode radio to transmit, monitoring the
direct mode channel for a response from the last radio to transmit,
and if a call grant granting the new call request is received from
the last radio to transmit, initiating the new direct mode call on
the direct mode communication channel. If the call grant is not
received, at least temporarily refraining from initiating the new
direct mode call.
[0019] In another embodiment, a process for resolving call
collisions in a digital conventional direct mode includes
transmitting, on a direct mode communication channel, one or more
transmissions during a first direct mode call to the other direct
mode radios in the plurality of direct mode radios, the
transmissions including an identifier identifying the first direct
mode radio, and after making the last transmission of the first
direct mode call, transitioning to an arbitrating mode and
monitoring the direct mode communication channel for any new direct
mode call requests from other direct mode radios in the plurality
of direct mode radios. While monitoring the direct mode channel,
receiving, from a second direct mode radio out of the plurality of
direct mode radios, a first new direct mode call request, and
continuing to monitor the direct mode communication channel for any
additional new direct mode call requests from other direct mode
radios in the plurality of direct mode radios. Responsive to
determining that (i) no other new direct mode call requests have
been received or (ii) other new direct mode call requests have been
received but the first new direct mode call request is entitled to
priority over the other new call requests: broadcasting a call
grant granting the first new direct mode call request of the second
direct mode radio, the call grant including an identifier
identifying the second direct mode radio, and receiving and playing
back content received from the second direct mode radio broadcast
over the direct mode communication channel during the first new
direct mode call granted by the acknowledgment.
[0020] Each of the above-mentioned embodiments will be discussed in
more detail below, starting with example network and device
architectures of the system in which the embodiments may be
practiced, followed by a discussion of resolving call collisions in
a digital conventional direct mode communication system from the
point of an initiating radio and then from the point of view of an
arbitrating/last transmitting radio. Further advantages and
features consistent with this disclosure will be set forth in the
following detailed description, with reference to the figures.
[0021] I. Network and Device Architectures
[0022] Referring now to FIG. 1, an example of a digital
conventional direct mode wireless communications system 100
comprising a plurality of radios 105 operating in accordance with
an embodiment is illustrated. Radios 105-1 through 105-5
communicate with each other on direct mode radio frequencies
without communicating through any infrastructure including, for
example, a repeater or base station. It will be appreciated by
those of ordinary skill in the art that in some embodiments the
frequency could also have repeaters on it, but radios 105 may not
use those repeaters (e.g., the repeaters could belong to a
different system, or the radios are operating in a talk-around
mode).
[0023] A radio, as used herein, can be mobile and/or fixed end
equipment that is used to obtain direct mode wireless
communications services. For example, a radio can be a mobile radio
(i.e. a portable radio, a mobile station, a subscriber unit, a
mobile subscriber), or can be a fixed station (i.e. a fixed control
station, a base station, and any supporting equipment such as
wireline consoles and packet data switches). Each radio is capable
of communicating directly with one or more other radios using
techniques as further described herein, such as TDMA, in which
specified time segments are divided into assigned time slots for
individual communications and each radio frequency (RF) in the
system carries time slots whereby each time slot is known as a
"channel." In the case of FDMA communications, channels may be
separated by frequency, and in CDMA communications, channels may be
separated by spreading code.
[0024] For ease of describing the embodiments hereinafter, the
digital conventional direct mode wireless communications system 100
is presumed to be a two time slot TDMA communications system in
accordance with the ETSI-DMR standard. Thus, in the embodiments
described below, since there are two time slots, there are two
channels available on each radio frequency for carrying the traffic
of the system. A time slot is an elementary timing of the physical
channel. For example, in one embodiment consistent with the
ETSI-DMR standard for repeater-based communications, a time slot
has a length of thirty milliseconds (30 ms) and is numbered "1" or
"2". In another example, and consistent with the ETSI-DMR direct
mode, only one of the two time slots is used for direct mode
communications, leaving one 27.5 ms timeslot numbered "1" (after
eliminating unnecessary 1.25 ms guard intervals). It is important
to note, however, that the TDMA communication system may have other
slot lengths and slotting ratios, as well.
[0025] As discussed above, and illustrated further in the
transmission diagram 200 of FIG. 2, within the present ETSI-DMR
direct mode systems, in the 12.5 KHz direct mode of operation,
radios transmit asynchronously (because there is no common time
slot reference available) and radios within range of the
transmission synchronize themselves to that transmission for the
purposes of receiving the transmission, but any transmissions in
response to the first transmission are transmitted asynchronously.
At present, and in one mode, there is an unused 32.5 ms portion 205
of the channel according to the standard (used in the repeater mode
for a 2.sup.nd timeslot/channel). In another mode, an additional
2.sup.nd timeslot/direct mode channel is provided in the unused
32.5 ms portion 205, and the radios transmit synchronously.
[0026] Radios 105-1-105-5 may directly communicate over a single
shared RF frequency in accordance with the ETSI-DMR standard. For
example, radio 105-1 in digital conventional direct mode
communication system 100 may initiate a new direct mode call 114 to
radios 105-2-105-5 on a timeslot 1 202, as illustrated in the
timing diagram 200 of FIG. 2. Timeslot 1 202 includes a 27.5 ms
payload period 214 that includes a sync slot 216. At substantially
the same time that radio 105-1 initiates its new call, radio 105-5
in digital conventional direct mode communication system 100 may,
having no knowledge of the direct mode call 114, similarly initiate
a new direct mode call 124 to radios 105-1-105-4 on the same direct
mode channel (e.g., during the same timeslot 1 202 of FIG. 2).
Assuming there is no arbitration on the channel, radio 105-1's and
radio 105-5's transmissions during a same time period would likely
corrupt each other, and as a result, radios 105-2-105-4 would not
receive either of the digital calls being transmitted by radios
105-1 and 105-5. FIGS. 4 and 5, below, illustrate (with respect to
FIGS. 1 and 2) a method for resolving this type of call collision
in digital conventional direct mode communications systems.
[0027] FIG. 3 is an example functional block diagram of a direct
mode radio, such as radio 105-1 operating within the system 100 of
FIG. 1 in accordance with some embodiments. Other direct mode
radios, such as radios 105-2-105-5, may contain same or similar
structures. As shown in FIG. 3, radio 105-1 includes a
communications unit 302 coupled to a common data and address bus
317 of a processing unit 303. The radio 105-1 may also include an
input unit (e.g., keypad, pointing device, etc.) 306, an output
transducer unit (e.g., speaker) 320, an input transducer unit
(e.g., a microphone) 321, and a display screen 305, each coupled to
be in communication with the processing unit 303.
[0028] The processing unit 303 may include an encoder/decoder 311
with an associated code Read Only Memory (ROM) 312 for storing data
for encoding and decoding voice, data, control, and/or other
signals that may be transmitted or received between other radios
within direct mode communication range of radio 105-1. The
processing unit 303 may further include a microprocessor 313
coupled, by the common data and address bus 317, to the
encoder/decoder 311, a character ROM 314, a Random Access Memory
(RAM) 304, and a static memory 316. The processing unit 303 may
also include a digital signal processor (DSP) 319, coupled to the
speaker 320, the microphone 321, and the common data and address
bus 317, for operating on audio signals received from one or more
of the communications unit 302, the static memory 316, and the
microphone 321.
[0029] The communications unit 302 may include an RF interface 309
configurable to communicate directly with other direct mode radios,
such as radios 105-2 to 105-5. The communications unit 302 may
include one or more wireless transceivers 308, such as a DMR
transceiver, an APCO P25 transceiver, a TETRA transceiver, a
Bluetooth transceiver, a Wi-Fi transceiver perhaps operating in
accordance with an IEEE 802.11 standard (e.g., 802.11a, 802.11b,
802.11g, 802.11n), a WiMAX transceiver perhaps operating in
accordance with an IEEE 802.16 standard, and/or other similar type
of wireless transceiver configurable to communicate via a wireless
network. The transceiver 308 is also coupled to a combined
modulator/demodulator 310 that is coupled to the encoder/decoder
311.
[0030] The microprocessor 313 has ports for coupling to the input
unit 306 and to the display screen 305. The character ROM 314
stores code for decoding and/or encoding data such as control
messages and/or data or voice messages that may be transmitted or
received by the radio 105-1. Static memory 316 may store operating
code for the microprocessor 313 that, when executed, monitors
direct mode communications, detects new call requests, identifies a
last radio to transmit, transmits a new call request for receipt by
the last radio to transmit, monitors for a response from the last
one of the other direct mode radios to transmit on the direct mode
communication channel, and acts accordingly based on whether or not
an acknowledgement of the call request is received from the last
one of the direct mode radios to transmit, in accordance with one
or more of FIGS. 4-5 and corresponding text. Static memory 316 may
additionally or alternatively store operating code for the
microprocessor 313 that, when executed, allows a last-to-transmit
radio to arbitrate and grant or not grant subsequent new call
requests in a direct mode communication channel in accordance with
one or more of FIGS. 4-5. Static memory 316 may comprise, for
example, a hard-disk drive (HDD), an optical disk drives such as a
compact disk (CD) drive or digital versatile disk (DVD) drive, a
solid state drive (SSD), a flash memory drive, or a tape drive, to
name a few.
[0031] II. The Process of Resolving Call Collisions in a Digital
Conventional Direct Mode
[0032] FIGS. 4-5 set forth examples of a method for resolving call
collisions in a digital conventional direct mode, from the point of
view of, and executable at, a new call initiating radio device
(FIG. 4) and then from the point of view of, and executable at, an
arbitrating/last transmitting radio device (FIG. 5). In the
following process flow diagrams, examples will be described with
respect to FIGS. 1 and 2, in which it is assumed that radios 105-1
to 105-5 are all on a same system (e.g., use the same color code or
other system identifier to distinguish their calls from other calls
that may also occur on a same direct mode frequency), 105-2 was the
last radio transmit on the system, and that radio 105-1 transmits a
new call request first.
[0033] FIG. 4 sets forth an example process flow 400 in which a new
call initiating radio device, perhaps radio 105-1 of FIG. 1, helps
to resolve call collisions in a digital conventional direct mode.
At step 402, an initiating direct mode radio monitors a direct mode
channel (e.g., frequency, time slot, and/or code) with which it is
associated for transmissions from other direct mode radios that
transmit with a same system (or group) identifier with which the
initiating direct mode radio is associated. For example, radio
105-1 monitors a direct mode TDMA channel for transmission from
other radios (e.g., 105-2 to 105-5) that identify with the same
system identifier or group identifier. In one embodiment, the
system identifier may be a color code, and the radio 105-1 may
monitor a direct mode TDMA channel for transmission from other
radios with a same color code as it is configured with (e.g., 0001,
0101, or 1111). In another embodiment, the system identifier may be
a group identifier such as a talkgroup identifier.
[0034] If a transmission is detected at step 402 from a radio on a
system or group as the monitoring radio, the initiating radio
decodes the transmission and locates a source ID for the
transmission (identifying the source radio), and records the source
ID in local storage as a last-transmitting radio. The source ID
could be a hardware identifier pre-provisioned into the radio
(perhaps in accordance with the DMR standard), a MAC address, an IP
address, or some other identifier capable of uniquely identifying
the radio doing the transmitting. The transmission containing the
source ID could be a link control (LC) burst, an embedded LC burst,
a voice header, a preamble control signaling block (CSBK), or any
other signaling, voice, or data burst that includes a source ID
identifying the transmitting radio. In some embodiments, call
request and call grant bursts are not considered in identifying the
last radio to transmit.
[0035] During the monitoring of step 402, transmissions received
that include a system identifier or talkgroup identifier that is
not associated with a same system identifier talkgroup with which
the initiating radio is associated may simply be discarded, without
recording or otherwise storing the identity of the radio doing the
transmitting.
[0036] At step 404, the initiating radio detects a request to
initiate a new direct mode call on the direct mode channel. For
example, direct mode radio 105-1 of FIGS. 1 and 3 may detect a
request to transmit a new direct mode call via a detected
activation of a PTT input 306 indicating a user's desire to
transmit a new direct mode call (perhaps as a function of an
indicated group or channel selected via a separate channel knob
input 306). Other types of inputs, including voice-activated or
touch-activated, could additionally or alternatively cause the
initiating radio to detect a request to initiate the new direct
mode call. Also at step 404, the direct mode radio sets an internal
retry counter to 0.
[0037] At step 406, and responsive to detecting the request to
initiate the new direct mode call, the initiating radio identifies
the last direct mode radio to transmit (e.g., the most recent or
immediately previous radio to transmit) on the direct mode channel.
In one embodiment, this may be the last direct mode radio to
transmit with a same system identifier or group identifier with
which the initiating radio is also associated, and may be a source
ID retrieved from storage after the monitoring at step 402. In some
embodiments in which there is no known last transmitting radio, or
the previously identified and/or stored last transmitting radio
actively has indicated that it is powering down or otherwise
leaving the area and would no longer be available to arbitrate
direct mode calls, the initiating radio may identify a transmitting
radio prior to the last transmitting radio, may identify itself as
the last transmitting radio, or may assign a random or
pseudo-random identifier as the last transmitting radio source ID.
Other possibilities exist as well.
[0038] At step 408, and assuming the direct mode channel is
currently idle, the initiating radio transmits a new call request
on the direct mode channel for receipt by the last known
transmitting radio that was identified at step 406. The request may
be, for example, a voice header or a preamble control signaling
block (CSBK), or any other signaling, voice, or data burst acting
as a new call request and populated with the source ID of the
identified last direct mode radio from step 406 as the target
device for the new call request. The request may be transmitted
directly to the last direct mode radio (e.g., identify the last
direct mode radio as a target of the request), or may be
transmitted or broadcast in some other manner for receipt by the
last direct mode radio (e.g., identify some other radio such as the
desired target radio for the new call, in which case the last radio
to transmit may still be configured to intercept and respond to
such a formatted request). Other examples are possible as well.
[0039] At step 410, the initiating radio switches from transmit
mode to receive mode and monitors the direct mode channel for a
response from the identified last direct mode radio (e.g., the
"arbitrating radio" for the direct mode call). At step 412, the
initiating direct mode radio determines if the arbitrating radio
granted its call request or not. For example, it may monitor the
direct mode channel for a call grant from the identified last
direct mode radio that includes the initiating radio's source ID.
In one embodiment, the call grant may be a repeated version of the
call request, with flipped source and destination identifiers, and
could be transmitted in the form of a call header or CSBK.
[0040] Assuming a call grant is received at step 412 granting the
initiating direct mode radio's new call request, processing
proceeds to step 414, where the initiating direct mode radio
transmits the new call on the direct mode channel. The new call may
be a private call (radio to radio), a group call (radio to group
via multicast or broadcast), or a broadcast call (radio to
all).
[0041] On the other hand, if the initiating direct mode radio does
not receive the call grant granting the requested new call at step
412 within some threshold period of time (such as between 60 and
180 ms, and in one embodiment, 120 ms), processing proceeds to step
416, where the initiating direct mode radio refrains from
initiating the new call for at least a temporary period of time
(e.g., until some further determination is made), up to a
configurable maximum period of time such as 180 ms. Further at step
416, the initiating direct mode radio may determine at step 416
whether a call grant is received that identifies some other radio
than the initiating direct mode radio, but e.g., with the same
system or group identifier as the initiating radio. For example,
the radio 105-1 may monitor the direct mode channel and see a call
grant (perhaps with a same color code of "0001" with which may be
associated) from arbitrating/last known transmitting radio 105-2
that identifies radio 105-5 as the target of the call grant. If it
is determined that a new call grant was transmitted granting a new
call to some radio other than the initiating radio, processing
proceeds to step 418, where the initiating direct mode radio
determines whether the call granted to the other radio is of
interest to the initiating direct mode radio (e.g., the grant
identifies a same color code and/or group with which the initiating
direct mode is associated or subscribed).
[0042] If the call is of interest, the initiating direct mode radio
joins the new call on the direct mode channel at step 420,
including receiving, decoding, and playing back content (e.g.,
voice, audio, and/or video) received via the direct mode channel,
and correspondingly updating the identity of the last radio to
transmit. At step 420, the radio may also provide some audio or
visual indication to its user, perhaps via a display such as screen
305 or speaker such as speaker 320, that the new call requested at
step 404 cannot be completed (e.g., was denied). On the other hand,
if it is determined that the call is not of interest to the
initiating direct mode radio at step 418, processing proceeds to
step 422, where the initiating direct mode radio refrains from
joining the new call, but may still provide some audio or visual
indication to its user, perhaps via the display or the speaker,
that the new call requested at step 404 cannot be completed, and
may still and correspondingly update the identity of the last radio
to transmit.
[0043] Returning to step 416, if it is determined that no other
call grants have been received on the direct mode channel, the
initiating direct mode radio may assume that there was some problem
in transmitting the new call request to the arbitrating radio, some
problem in the arbitrating radio processing the request, or some
problem in receiving the call grant at the initiating radio, among
other possibilities. Processing thus proceeds to step 424, where
the initiating radio determines whether a maximum number of retries
has been reached. For example, if the identified last direct mode
radio is known at step 406, the maximum number of retries may be in
the range of 2-5. On the other hand, if the identified last direct
mode radio is not known, or the last direct mode radio actively
withdrew its arbitrator status, the maximum number of retries may
be reduced to the range of 1-3. In any event, if the maximum number
of retries has been reached at step 424 (e.g., the retry counter is
equal to or greater than the maximum), processing proceeds to step
414, where the initiating direct mode radio initiates the new call
on the direct mode channel despite the non-receipt of a call grant
from a known or unknown arbitrating radio (and assuming that the
channel is determined to be clear).
[0044] Returning to step 424, if it is determined that the maximum
number of retries has not been reached, processing proceeds to step
426, where the retry counter is incremented and a random delay
(configurable and preferably within the range of 0 to 720 ms)
applied before proceeding back to step 408 and re-transmitting the
new call request to the identified last direct mode radio. The
random delay (back-off) applied at step 426 is intended to prevent
a recurrence of interference between two initiating direct mode
radios that may have caused the last new call request transmitted
at step 408 to not be fully or accurately received by the last
transmitting direct mode radio.
[0045] FIG. 5 sets forth an example process flow 500 in which an
arbitrating/last transmitting radio device helps to resolve call
collisions in a digital conventional direct mode communications
system. At step 502, the arbitrating direct mode radio transmits a
first call on a direct mode channel. At step 504, and after making
the last transmission of the first call, the arbitrating direct
mode radio transitions to an arbitrator role by switching to a
receive mode while tuned to the direct mode channel and monitoring
the direct mode channel for any new direct mode call requests from
other direct mode radios that transmit with a same system (or
group) identifier with which the arbitrating direct mode radio is
associated. Also at step 504, and while in the receive mode, the
arbitrating direct mode radio receives a first new call request on
the direct mode channel, addressed to the arbitrating direct mode
radio or some other radio, and including a source ID identifying
the requesting (e.g., initiating) direct mode radio.
[0046] At step 506, the arbitrating direct mode radio continues to
monitor the direct mode channel for a period of time (up to a
configurable maximum period of time such as 180 ms) to determine
whether any additional new call requests have been transmitted. For
example, the arbitrating direct mode radio may continue monitoring
the direct mode channel for 120 ms to aid in preventing a collision
of call grant with a delayed call request from another radio. While
acting as an arbitrator at step 506, and in response to one of a
received instruction to power-off or otherwise disable its
transceiver, or in response to an error condition indicative of an
inability to receive transmissions over the direct mode
communications channel, the arbitrating direct mode radio may
broadcast an announcement indicating that the radio will no longer
be available to arbitrate new call requests on the direct mode
channel.
[0047] At step 508, the arbitrating direct mode radio determines
whether any other new call requests were received. If not,
processing continues to step 510, where the arbitrating direct mode
radio broadcasts a call grant granting the first new call request
to the requesting direct mode radio. On the other hand, if
additional other new call requests were received at step 508,
processing proceeds to step 512, where the arbitrating direct mode
radio arbitrates between the two or more new call requests
received. The arbitrating direct mode radio may use any number of
known techniques for determining which call to grant, including
considering an order in which the requests were received (giving
higher priority to earlier arriving requests), a priority
associated with a particular radio (perhaps pre-stored at the
arbitrating direct mode radio, based on a radio ID included in the
request), a priority associated with a talkgroup to which the new
call request is directed (again, perhaps pre-stored at the
arbitrating direct mode radio, based on a radio ID included in the
request), based on the type of call requested (emergency vs.
non-emergency, group vs. private, etc.), or some other system or
radio attribute. Assuming that the first new call request is
determined at step 512 as entitled to priority over the other new
call requests received at step 506, processing proceeds to step
510, where the arbitrating direct mode radio broadcasts a call
grant granting the first new call request to the requesting direct
mode radio, the call grant identifying a source ID of the
requesting direct mode radio.
[0048] At step 514, the arbitrating direct mode radio determines
whether it is interested in the granted first new call (perhaps in
a manner similar to step 418 of FIG. 4), and if so, receives and
plays back the content received from the requesting first direct
mode radio over the direct mode channel, and correspondingly
updates the identity of the last radio to transmit, at step 516.
If, on the other hand, the arbitrating direct mode radio determines
that it is not interested in the granted first new call, it
refrains from receiving, decoding, and/or playing back the content
transmitted by the first direct mode radio, but may still
correspondingly update the identity of the last radio to
transmit.
[0049] In the foregoing specification, specific embodiments have
been described. However, one of ordinary skill in the art
appreciates that various modifications and changes can be made
without departing from the scope of the invention as set forth in
the claims below. Accordingly, the specification and figures are to
be regarded in an illustrative rather than a restrictive sense, and
all such modifications are intended to be included within the scope
of present teachings.
[0050] The benefits, advantages, solutions to problems, and any
element(s) that may cause any benefit, advantage, or solution to
occur or become more pronounced are not to be construed as a
critical, required, or essential features or elements of any or all
the claims. The invention is defined solely by the appended claims
including any amendments made during the pendency of this
application and all equivalents of those claims as issued.
[0051] Moreover in this document, relational terms such as first
and second, top and bottom, and the like may be used solely to
distinguish one entity or action from another entity or action
without necessarily requiring or implying any actual such
relationship or order between such entities or actions. The terms
"comprises," "comprising," "has", "having," "includes",
"including," "contains", "containing" or any other variation
thereof, are intended to cover a non-exclusive inclusion, such that
a process, method, article, or apparatus that comprises, has,
includes, contains a list of elements does not include only those
elements but may include other elements not expressly listed or
inherent to such process, method, article, or apparatus. An element
proceeded by "comprises . . . a", "has . . . a", "includes . . .
a", "contains . . . a" does not, without more constraints, preclude
the existence of additional identical elements in the process,
method, article, or apparatus that comprises, has, includes,
contains the element. The terms "a" and "an" are defined as one or
more unless explicitly stated otherwise herein. The terms
"substantially", "essentially", "approximately", "about" or any
other version thereof, are defined as being close to as understood
by one of ordinary skill in the art, and in one non-limiting
embodiment the term is defined to be within 10%, in another
embodiment within 5%, in another embodiment within 1% and in
another embodiment within 0.5%. The term "coupled" as used herein
is defined as connected, although not necessarily directly and not
necessarily mechanically. A device or structure that is
"configured" in a certain way is configured in at least that way,
but may also be configured in ways that are not listed.
[0052] It will be appreciated that some embodiments may be
comprised of one or more generic or specialized processors (or
"processing devices") such as microprocessors, digital signal
processors, customized processors and field programmable gate
arrays (FPGAs) and unique stored program instructions (including
both software and firmware) that control the one or more processors
to implement, in conjunction with certain non-processor circuits,
some, most, or all of the functions of the method and/or apparatus
described herein. Alternatively, some or all functions could be
implemented by a state machine that has no stored program
instructions, or in one or more application specific integrated
circuits (ASICs), in which each function or some combinations of
certain of the functions are implemented as custom logic. Of
course, a combination of the two approaches could be used.
[0053] Moreover, an embodiment can be implemented as a
computer-readable storage medium having computer readable code
stored thereon for programming a computer (e.g., comprising a
processor) to perform a method as described and claimed herein.
Examples of such computer-readable storage mediums include, but are
not limited to, a hard disk, a CD-ROM, an optical storage device, a
magnetic storage device, a ROM (Read Only Memory), a PROM
(Programmable Read Only Memory), an EPROM (Erasable Programmable
Read Only Memory), an EEPROM (Electrically Erasable Programmable
Read Only Memory) and a Flash memory. Further, it is expected that
one of ordinary skill, notwithstanding possibly significant effort
and many design choices motivated by, for example, available time,
current technology, and economic considerations, when guided by the
concepts and principles disclosed herein will be readily capable of
generating such software instructions and programs and ICs with
minimal experimentation.
[0054] The Abstract of the Disclosure is provided to allow the
reader to quickly ascertain the nature of the technical disclosure.
It is submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims. In addition,
in the foregoing Detailed Description, it can be seen that various
features are grouped together in various embodiments for the
purpose of streamlining the disclosure. This method of disclosure
is not to be interpreted as reflecting an intention that the
claimed embodiments require more features than are expressly
recited in each claim. Rather, as the following claims reflect,
inventive subject matter lies in less than all features of a single
disclosed embodiment. Thus the following claims are hereby
incorporated into the Detailed Description, with each claim
standing on its own as a separately claimed subject matter.
* * * * *