U.S. patent application number 11/226485 was filed with the patent office on 2006-03-23 for transparent broadcast structure in communication systems.
Invention is credited to Peter de Bruin, Tor Bjorn Minde, Arne Simonsson.
Application Number | 20060062179 11/226485 |
Document ID | / |
Family ID | 36073852 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060062179 |
Kind Code |
A1 |
Simonsson; Arne ; et
al. |
March 23, 2006 |
Transparent broadcast structure in communication systems
Abstract
A broadcast channel, such as a broadcast control channel that
carries a short message service, in a GSM/EDGE or similar
communication system can be extended with additional timeslots.
These additional timeslots can be pointed out in a tree structure,
the root of which is in the SMS broadcast channel. The extended
broadcast channel can be used for broadcast-like services provided
under a multimedia broadcast/multicast service.
Inventors: |
Simonsson; Arne;
(Gammelstad, SE) ; Minde; Tor Bjorn; (Gammelstad,
SE) ; Bruin; Peter de; (Gammelstad, SE) |
Correspondence
Address: |
POTOMAC PATENT GROUP, PLLC
P. O. BOX 270
FREDERICKSBURG
VA
22404
US
|
Family ID: |
36073852 |
Appl. No.: |
11/226485 |
Filed: |
September 14, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60612161 |
Sep 23, 2004 |
|
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Current U.S.
Class: |
370/328 |
Current CPC
Class: |
H04W 72/005 20130101;
H04W 4/06 20130101; H04W 4/14 20130101 |
Class at
Publication: |
370/328 |
International
Class: |
H04Q 7/00 20060101
H04Q007/00 |
Claims
1. A channel structure configured for distribution of multimedia
information in a communication system, comprising: a broadcast
communication channel divided into a plurality of timeslots; and a
pointer included in a predetermined one of the timeslots, the
pointer pointing out at least one extension channel that is
included in at least one other broadcast timeslot and that carries
unacknowledged multimedia information.
2. The channel structure of claim 1, wherein the communication
channel is a broadcast control channel (BCCH) and the at least one
other timeslot is included in the BCCH.
3. The channel structure of claim 2, wherein the pointer is a
character string included in a timeslot zero.
4. The channel structure of claim 2, wherein the BCCH includes a
short message service (SMS) channel.
5. The channel structure of claim 1, wherein the pointer includes
hidden information that comprises at least one of a modulation and
coding scheme used on an extension channel and information on which
timeslot corresponds to which broadcast channel.
6. The channel structure of claim 1, wherein the plurality of
timeslots on the broadcast communication channel include a
plurality of extension channels, and the extension channels are
arranged in a tree structure having a root in the timeslot that
includes the pointer.
7. The channel structure of claim 6, wherein a first extension
channel pointed to by the pointer carries service guide
information.
8. The channel structure of claim 1, wherein multimedia information
carried by the extension channels comprises at least one of
off-line information and streaming television programs, and service
guide information that includes television program information.
9. The channel structure of claim 8, wherein the off-line content
is carried by an extension channel as a plurality of frames and
each frame includes at least one of forward error correction and an
error detection element.
10. A radio access network configured for distribution of
multimedia information, comprising: a base station that broadcasts
radio signals having a channel structure configured for the
multimedia information, wherein the radio channel structure
includes a broadcast communication channel divided into a plurality
of timeslots, and a predetermined one of the timeslots includes a
pointer that points out at least one extension channel that is
included in at least one other timeslot in the radio signals and
that carries unacknowledged multimedia information.
11. The radio access network of claim 10, wherein multimedia
information carried by at least one of the extension channels
comprises at least one of off-line information and streaming
television programs, and service guide information that includes
television program information.
12. The radio access network of claim 11, wherein the off-line
content is carried by an extension channel as a plurality of frames
and each frame includes at least one of forward error correction
and an error detection element.
13. A user equipment for a communication system in which a
broadcast signal includes a succession of timeslots that carry
unacknowledged multimedia information, comprising: an input device
configured for activation by a user; a receiver configured to
decode the broadcast signal, wherein a predetermined one of the
timeslots includes a pointer that points out at least one extension
channel that is included in at least one other timeslot of a
broadcast signal; and a control processor in communication with the
input device and the receiver; wherein, based on user-input
information from the input device and information about the
communication network, the control processor determines at least
one timeslot to receive and decode and causes the receiver to
receive and decode the determined timeslot.
14. The user equipment of claim 13, wherein the broadcast signal
includes a broadcast control channel (BCCH) and the at least one
other timeslot is included in the BCCH.
15. The user equipment of claim 14, wherein the pointer includes
hidden information that comprises at least one of a modulation and
coding scheme used on an extension channel and information on which
timeslot corresponds to which broadcast channel.
16. The user equipment of claim 13, wherein the receiver includes a
front end receiver that is turned on only during the determined
timeslot.
17. The user equipment of claim 13, wherein the determined timeslot
comprises at least one of off-line information, streaming
television programs, and service guide information selected by the
user through the input device.
18. The user equipment of claim 17, wherein the user equipment
further includes a memory configured to store unacknowledged
multimedia information; the off-line content is carried by an
extension channel as a plurality of frames; each frame includes at
least one of forward error correction and an error detection
element; and correctly decoded off-line content is stored in the
memory.
19. A method of distributing multimedia information in a
communication system, comprising: dividing a broadcast
communication channel into a plurality of timeslots; and including
a pointer in a predetermined one of the timeslots, wherein the
pointer points out at least one extension channel that is included
in at least one other timeslot of a broadcast communication channel
and that carries unacknowledged multimedia information.
20. The method of claim 18, wherein the broadcast communication
channel is a broadcast control channel (BCCH) and the at least one
other timeslot is included in the BCCH.
21. The method of claim 19, wherein the pointer is a character
string included in a timeslot zero.
22. The method of claim 19, wherein the BCCH includes a short
message service (SMS) channel.
23. The method of claim 18, wherein the including step comprises
the step of including hidden information in the pointer, and the
hidden information comprises at least one of a modulation and
coding scheme used on an extension channel and information on which
timeslot corresponds to which broadcast channel.
24. The method of claim 18, wherein the plurality of timeslots
include a plurality of extension channels, and the dividing step
comprises the step of arranging the extension channels in a tree
structure having a root in the timeslot that includes the
pointer.
25. The method of claim 24, wherein a first extension channel
pointed to by the pointer carries service guide information.
26. The method of claim 19, wherein unacknowledged multimedia
information carried by the at least one extension channel comprises
at least one of off-line information and streaming television
programs, and service guide information that includes television
program information.
27. The method of claim 26, wherein the off-line content is carried
by an extension channel as a plurality of frames and each frame
includes at least one of forward error correction and an error
detection element.
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application No. 60/612,161, filed on Sep. 23, 2004, which is
incorporated in its entirety here by reference.
BACKGROUND
[0002] This application relates to mobile communication systems and
in particular to television broadcasting in such communication
systems.
[0003] "Broadcast-like" television (TV) services, which is to say,
services with a conventional-television-channel concept, are
already available for some mobile telephony networks. For example,
the Mobile TV service of Telecom Italia Mobile (TIM) provides TIM
subscribers with streaming content, enabling subscribers to watch
TV shows on their mobile phones via GSM's general packet radio
service (GPRS) technology. Another example is sports-team goal
notification services, such as that provided by Vodafone, which
uses GSM's multimedia messaging service (MMS). These current
implementations are based on real-time streaming over unicast GPRS
bearers, but capacity limits on application servers and core and
radio access networks constrain service expansion and build-out. A
few network operators currently deliver broadcast-like services in
wideband code division multiple access (WCDMA) communication
systems by circuit-switched (CS) streaming.
[0004] A multimedia broadcast/multicast service (MBMS) in GSM and
WCDMA communication systems is currently standardized by the Third
Generation Partnership Project (3GPP) in Technical Specification
(TS) 23.246 "Multimedia Broadcast/Multicast Service (MBMS);
Architecture and functional description", V6.6.0, Rel. 6 (March
2003). According to the specification, MBMS is a
point-to-multipoint service, in which data is transmitted from a
single source entity to multiple recipients. Transmitting the same
data to multiple recipients allows network resources to be shared,
and the MBMS bearer service has broadcast and multicast modes. With
MBMS, a complete set of multicast and broadcast services can be
offered in telecommunication systems, such as UMTS and mobile
telephony systems according to the GSM, Enhanced Data Rates for GSM
Evolution (EDGE), and WCDMA specifications. The GSM EDGE radio
access network is usually abbreviated as GERAN. Changes to network
architecture as well as additional service-related signaling will
be introduced to the existing systems by deployment of MBMS.
Aspects of MBMS are described in M. Bakhuizen et al., "Mobile
Broadcast/Multicast in Mobile Networks", Ericsson Review vol. 82,
no. 1, pp. 6-13 (2005).
[0005] Audio and video coder/decoders (codecs) used for streaming
sessions for the small display screens typical of handheld devices
are improving and are standardized by the 3GPP, e.g., TS 26.234
"Transparent end-to-end Packet-switched Streaming Service (PSS);
Protocols and codecs", V6.3.0, Rel. 6 (March 2003). Current
implementations like the TIM Mobile TV service use streams that
have data rates of 28 kilobits per second (kbps), but for very high
quality content, the data rate needed is probably more than 100
kbps. For an intermediate level of quality, a data rate of 40-64
kbps is needed for a stream comprising both audio and video. For
example, 12 kbps could be used for stereo audio encoded according
to an adaptive multi-rate wideband codec (AMR-WB+) and 32 kbps for
video encoded according to an MPEG-4 codec. Considering user
sensitivity to errors in such streams, a block error rate (BLER) of
1%-2% or less may be needed for acceptable performance.
[0006] Another ongoing standardization activity is the Digital
Video Broadcasting (DVB) Project, which aims at including DVB
receivers in mobile terminals, such as mobile telephones. A recent
standard is "Digital Video Broadcasting (DVB); Transmission System
for Handheld Terminals (DVB-H)", ETSI EN 302 304 V1.1.1 (June
2004). This is an extension of the current DVB-terrestrial (DVB-T)
standard to support handheld devices and introduces a new
transmission mode, IP datacasting (IPDC), which is described in
"IPDC in DVB-H: Technical requirements", DVB Project (June 2004).
IPDC is the end-to-end DVB system, including a mobile interaction
channel for mobile handheld broadcast services. See also "IP
Datacast Baseline Specification; PSI/SI Guidelines for DVB-T/H
Systems", document A079, DVB Project (April 2004). For even more
information, the interested reader is directed to
http://www.dvb.org.
[0007] Moreover, inclusion of a separate DVB-H receiver in a user
terminal also requires new terminal hardware and antennas.
Different antennas might be needed in different countries due to
spectrum allocations. Interoperability testing and verification due
to new network nodes will delay introduction. Local distribution of
programs/channels will be costly due to needed modifications of
network structure, which is typically designed for national or
regional coverage.
[0008] Compared with DVB-H and DVB-T, GERAN/UTRAN MBMS has a lower
data rate. On the other hand, GERAN/UTRAN MBMS can transmit
different information in each cell. Thus, GERAN/UTRAN MBMS is
suitable for broadcasting content that is locally variable or
broadcast/multicast-group dependent. UTRAN, or the UMTS Terrestrial
Radio Access Network, is part of the Universal Mobile
Telecommunication System (UMTS) and identifies the part of the
network that includes radio network controllers (RNCs) and
so-called Node Bs, which are analogous to base stations in other
mobile telephone systems. UMTS is one of the third generation (3G)
mobile telephone systems being developed within the IMT-2000
framework of the International Telecommunications Union (ITU) and
standardized by the 3GPP.
[0009] Even so, to be competitive with DVB-H, the performance of
cellular broadcast bearers can stand improvement. Dedicated unicast
channels in either Enhanced GPRS (EGPRS) or WCDMA systems are
difficult to use for mobile TV streaming because such channels will
not scale to large usage. This problem of capacity limitations in
the radio network is helped by MBMS, which provides one dedicated
channel for each group of terminals receiving the same content.
Nevertheless, a separate channel for a program guide or service
description is also needed. Channel switching may also be slow with
the currently standardized MBMS due to delays caused by restart of
streaming sessions.
SUMMARY
[0010] In accordance with an aspect of this invention, a channel
structure configured for distribution of multimedia information in
a communication system is provided. The channel structure includes
a broadcast communication channel divided into a plurality of
timeslots; and a pointer included in a predetermined one of the
timeslots. The pointer points out at least one extension channel
that is included in at least one other broadcast timeslot and that
carries unacknowledged multimedia information.
[0011] In accordance with another aspect of this invention, a radio
access network configured for distribution of multimedia
information is provided. The radio access network includes a base
station that broadcasts radio signals having a channel structure
configured for the multimedia information, wherein the radio
channel structure includes a broadcast communication channel
divided into a plurality of timeslots, and a predetermined one of
the timeslots includes a pointer that points out at least one
extension channel that is included in at least one other timeslot
in the radio signals and that carries unacknowledged multimedia
information
[0012] In accordance with yet another aspect of this invention, a
user equipment for a communication network in which a broadcast
signal includes a succession of timeslots that carry unacknowledged
multimedia information is provided. The user equipment includes an
input device configured for activation by a user; a receiver
configured to decode the broadcast signal, and a control processor
in communication with the input device and the receiver. A
predetermined one of the timeslots includes a pointer that points
out at least one extension channel that is included in at least one
other timeslot of a broadcast signal. Based on user-input
information from the input device and information about the
communication network, the control processor determines at least
one timeslot to receive and decode and causes the receiver to
receive and decode the determined timeslot.
[0013] In accordance with a further aspect of this invention, a
method of distributing multimedia information in a communication
system is provided. The method includes the steps of dividing a
broadcast communication channel into a plurality of timeslots; and
including a pointer in a predetermined one of the timeslots. The
pointer points out at least one extension channel that is included
in at least one other timeslot of a broadcast communication channel
and that carries unacknowledged multimedia information.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The several features, objects, and advantages of this
invention will be understood by reading this description in
conjunction with the drawings, in which:
[0015] FIG. 1 depicts a broadcast channel having a plurality of
timeslots;
[0016] FIG. 2 is a block diagram of a communication system;
[0017] FIG. 3A is a block diagram of a radio access network in a
communication system;
[0018] FIG. 3B is a block diagram of a base station in a radio
access network;
[0019] FIG. 4 is a block diagram of a mobile terminal;
[0020] FIG. 5 is a more detailed block diagram of a mobile
terminal; and
[0021] FIG. 6 is a flow chart of a method of distributing
multimedia information.
DETAILED DESCRIPTION
[0022] The inventors have recognized that the existing short
message service (SMS) broadcast channel that is typically carried
by timeslot zero (TS0) on a broadcast control channel (BCCH) in a
GSM/EDGE or similar communication system can be extended with
additional timeslots and that these additional timeslots can be
pointed out in a tree structure, the root of which is in the SMS
broadcast channel. A BCCH typically carries overhead messages,
e.g., paging or call alert messages, as well as text messages like
SMS, directed to individual terminals.
[0023] The inventors have also recognized that such an extended
BCCH can be used for broadcast-like services and that it has no
need for interaction between communication terminals, such as
mobile telephones, and the infrastructure part of the communication
system, such as base stations or Node Bs. A terminal receives only
the broadcast channels that the base station transmits, and each
broadcast channel carries unacknowledged multimedia information. In
this way, ordinary EGPRS channels can be set up from a media server
to the broadcast channels in the base stations. The number of
channels, channel content, and the channel structure can be defined
by a system operator by suitable dimensioning and program
production. A terminal can select a broadcast channel and buffer or
download broadcast content with a suitable software application
executing in the terminal. Content may be buffered, or cached, for
shorter times to compensate for network latency, decoder delay,
etc., or downloaded for longer times to enable "off-line" or
non-real-time presentation of broadcast content. Buffering, or
caching, real-time multimedia streaming content can minimize
glitches in the data transfer and also channel switching time by
having several receive buffers filled up all the time. Also, the
same or another software application can select the best frequency
to receive, and thus in effect cause a handover of the
terminal.
[0024] FIG. 1 depicts a plurality of timeslots TS0, TS1, TS2, . . .
, TS7 that are temporal portions of a carrier signal. In GSM/EDGE,
TS0 of the BCCH carries SMS information, and an SMS broadcast
channel may carry 15 pages with 93 characters.
[0025] The inventors have understood that a pointer or token, such
as a character string, that points out an extension channel can be
inserted in a timeslot, such as in any of the pages broadcast on a
typical SMS channel. For example, the string, "Broadcast: BCCH TS1:
BBC", could be inserted into a page carried by TS0. As suggested by
the string itself and as described in more detail below, such a
string can point to another BCCH timeslot or timeslots and indicate
information to be found there. In this example, timeslot TS1 of the
BCCH has information about a British Broadcasting Corporation (BBC)
channel.
[0026] It will be appreciated that any suitable pointer can be
used, not merely a character string, and that the pointer need only
be included in a predetermined slot on virtually any broadcast
channel. Moreover, the pointer need not point to a slot or slots on
its own channel, but in general can point to any other slot or
slots transmitted in the communication system. In addition, the
pointer can include information that is "open", i.e., presented to
a user, and information that is "hidden", i.e., information that is
used by the user's equipment but need not be presented to the user.
Some examples of such hidden information are information on the
modulation and coding scheme used for a broadcast channel or
channels, and information on which timeslot corresponds to which
broadcast channel.
[0027] As in the example shown by FIG. 1, the first extension
channel carried in a timeslot such as timeslot TS1 and indicated by
a pointer such as an SMS character string can advantageously be a
service or program guide, which may conveniently but not
necessarily look similar to a main page of a conventional text-TV
channel. By providing a sufficient number of physical timeslots for
the extension channel, several main pages or channels can be
pointed out, for example one for each broadcast service node or
broadcast production available from the communication system. Three
such main pages in timeslot TS1 are indicated by the three arrows
that point to respective pairs of subsequent timeslots. It is
advantageous for the content of a Service Guide to be continuously
updated to the terminal.
[0028] One or more suitable pointers such as character strings on a
main page can point to another extension channel or channels, which
are carried by the additional timeslot(s) pointed out. In the
example shown in FIG. 1, an extension channel called TV channel1 is
carried by timeslots TS2 and TS3, another extension channel called
TV channel2 is carried by timeslots TS4 and TS5, and yet another
extension channel called TV channel3 is carried by timeslots TS6
and TS7. Thus, the whole BCCH is indicated as allocated for
broadcast channels, but this is not necessary. Moreover, the
channels carrying the unacknowledged multimedia information, such
as the Service Guide and three TV channels in this example, can be
arranged in any suitable way among the allocated timeslots.
[0029] FIG. 2 is a block diagram of a communication system 200 that
can employ the channel structures described in this application. A
mobile terminal, or user equipment (UE) 202, communicates through a
radio access network (RAN) 204, such as GSM/EDGE, with core-network
entities, including a servicing GPRS support node (SGSN) 206, a
gateway GSN (GGSN) 208, a home location register (HLR) 210, and a
broadcast/multicast service center (BM-SC) 212. The core-network
entities are conventional and adapted to handle MBMS and multimedia
information generally. In a typical GSM/EDGE network, a PDP Context
for administering data flows is set up in the GGSN 208 in response
to a request from the terminal/UE 202.
[0030] In particular, the BM-SC 212 is responsible for providing
and delivering mobile broadcast services, and serves as an entry
point for content-delivery services or servers that want to use
MBMS. It sets up and controls MBMS transport bearers to the RAN 204
and can be used to schedule and deliver MBMS transmissions. The
BM-SC 212 can also provide service announcements to UEs that
contain information needed to join an MBMS service. The BM-SC 212
can be used to manage security functions specified for multicast
mode. The RAN 204 includes one or more base stations and base
station controllers, or Node Bs and radio network controllers
(RNCs), that are conventional except to the extent that the radio
signals transmitted toward the UE include the channel structures
described in this application.
[0031] FIG. 3A depicts the RAN 204 in more detail. Radio network
controllers (RNCS) 302, 304 control various radio network
functions, including for example radio access bearer setup,
diversity handover, etc. More generally, each RNC directs calls to
and from a terminal/UE via the appropriate BSs, which communicate
with each other through downlink (i.e., base-to-mobile or forward)
and uplink (i.e., mobile-to-base or reverse) channels. In FIG. 3A,
RNC 302 is shown coupled to BSs 306, 308, 310, and RNC 304 is shown
coupled to BSs 312, 314, 316.
[0032] Each BS, or Node B in 3G vocabulary, serves a geographical
area that is divided into one or more cell(s). In FIG. 3A, BS 316
is shown as having five antenna sectors S1-S5, which can be said to
make up the cell of the BS 316, although a sector or other area
served by signals from a BS can also be called a cell. The BSs are
typically coupled to their corresponding RNCs by dedicated
telephone lines, optical fiber links, microwave links, etc. The
RNCs 302, 304 are connected with external networks such as the
public switched telephone network (PSTN), the internet, etc.
through one or more core-network entities.
[0033] As UEs move with respect to the BSs, and possibly vice
versa, on-going connections are maintained through a process of
handover, or hand-off, in which as a user moves from one cell to
another, the user's connection is handed over from one BS to
another. In FIG. 3A, UEs 318, 320 are shown communicating with
plural BSs in diversity handover situations. UE 318 communicates
with BSs 306, 308, 310, and UE 320 communicates with BSs 310, 312.
A control communication link between the RNCs 312, 314 permits
diversity communications to/from the UE 320 via the BSs 310,
312.
[0034] FIG. 3B is a block diagram of the base station 306 that
shows portions of the BS involved in generating the BCCH as
described in this application. It will be appreciated that FIG. 3B
shows an arrangement that is typical of base stations in the
communication system 200. A base station includes a number of
transceiver units for two-way communication with UEs in the system,
and FIG. 3B indicates these transceiver units TRU-1, TRU-2, TRU-3,
. . . , TRU-N. In principle, the number of transceiver units is not
restricted; it may even be zero.
[0035] Each TRU is typically allocated a respective "channel
group", which is a set of downlink and possibly uplink radio
carrier signals having frequencies planned with a given frequency
reuse pattern in the system. In FIG. 3B, the transceiver unit
TRU-1, for example, can belong to the channel group "BCCH" and the
other transceiver units can belong to the channel group "TCH", or
"traffic channel". Alternatively, there can be a number of
different TCH channel groups, with one or more of the transceiver
units belonging to each of the different groups, thereby enabling
the different TCH groups to be planned with different frequency
reuse patterns.
[0036] A transceiver unit advantageously (but not necessarily)
includes all functionality needed for handling radio signals in the
communication system, e.g., the eight time slots in a time-division
multiple-access (TDMA) frame like that depicted by FIG. 1,
including timing reference generation, signal processing, radio
receiving, and transmitting and power amplification. Thus, a
transceiver unit typically includes radio transmitting and
receiving components that are controlled by and provide signals to
and from one or more processors. For example, a transceiver unit
can generate a signal having a plurality of frames, and each frame
can include at least one of forward error correction and an error
detection element through suitable operation of the transceiver's
signal processing and other functionality, which may include
suitable processing resources for enciphering/deciphering
signals.
[0037] As indicated in FIG. 3B, signals to and from the transceiver
units pass through a combiner 322 on their ways to or from the base
station's antenna 324. The combiner 322 combines transmitted
signals from the several transceiver units and distributes received
signals to the transceiver units.
[0038] Thus, it will be understood that the TRU in the BCCH channel
group formulates radio-frequency signals that are provided to the
antenna 324. The signals have a channel structure configured for
multimedia information, including a broadcast communication
channel, e.g., a BCCH, divided into a plurality of timeslots. As
indicated for example by FIG. 1, a predetermined one of the
timeslots includes a pointer that points out at least one extension
channel that is included in at least one other timeslot in the
radio signals and that carries unacknowledged multimedia
information.
[0039] It is currently believed for system capacity reasons that
the BCCH is suitable for carrying broadcast channels in this way.
The BCCH is used for handover measurements and so the BCCH is
continuously transmitted and cell planning is made with a high
frequency-reuse factor. The already continuous broadcast of the
BCCH carrier means that adding broadcast capability to a system
would not increase the activity factor or interference level. Radio
signal quality or received signal strength will also typically be
good at cell borders.
[0040] It will be understood, however, that BCCH channels are not
the only possibility for broadcast-like information as described
above. Carriers used for TCHs in the RAN can also be used. Even if
a TCH has lower radio quality and a lower timeslot bit rate than a
BCCH, more timeslots can easily be used to obtain comparable
service.
[0041] A system operator can determine the number of timeslots,
service, and quality of its broadcasts by suitable dimensioning.
The modulation and coding scheme (MCS) for transmission in the RAN
may be chosen based on desired quality, coverage, and frequency
plan, and the number of channels allocated for broadcast may be
based on capacity and desired service requirement, e.g., the codec
bit rate for the desired broadcast TV service. A number of
different schemes (MCS-1 to MCS-9) are currently standardized for
EGPRS. MCS-1 to MCS4 use Gaussian minimum shift keying (GMSK)
modulation, and MCS-5 to MCS-9 use (3.pi./8) 8-ary phase shift
keying (8-PSK) modulation.
[0042] As discussed above, an advantage of this arrangement is the
absence of a requirement for special interaction between a terminal
and a base station. The base station need only continuously
transmit unacknowledged multimedia information, and can be unaware
of a receiver's position or activation. The terminal selects a
channel of the broadcast information and also advantageously
selects the best transmitter of that information.
[0043] FIG. 4 is a block diagram of a mobile terminal or UE 202. To
facilitate selection of broadcast information, a software
application executed by a processor 402 in the terminal 202 may
advantageously re-define the terminal's keypad 404. The software
application may be stored in a suitable application memory 406 and
operate for example such that "1" on the keypad means channel 1,
which is then the Service Guide in the arrangement depicted in FIG.
1. This is described in more detail below.
[0044] The terminal 202 may also download and/or cache desired
information in a suitable memory 408 based on user preferences and
terminal applications. With cached information, instant channel
switching between broadcast TV channels can be done because a
streaming buffer need not be initiated. Either all broadcast
channels can be downloaded and/or cached or one or more channels
can be downloaded and/or cached according to user configuration or
previous usage. Non-real time transmissions, e.g., news clips, may
be downloaded and dynamically updated via the Service Guide to be
viewed at the user's convenience. Time-stamping and storage refresh
would then possibly be needed, as well as Service Guide updating.
For example, a Service Guide update can be sent with new content
(that is described in the update), a respective memory pointer, and
a time stamp. The new content can be presented on the broadcast
channels and the pointer to the new content can be presented in the
Service Guide. In this way, a larger amount of data (clips) can be
offered per timeslot without any change in user access delay since
the refresh rate can be increased. Although some content may not be
real-time and may be viewed at the user's convenience, such content
can still be updated with current information.
[0045] In the simplest form of this arrangement, it is not
necessary specially to select the "best" base station, and thus no
special control signaling is necessary. The typical cell selection
that is carried out for handling connection handovers should be
sufficient to ensure adequate operation. Besides cell selection,
another approach to ensuring that a terminal receives a suitable
broadcast signal is to use macro diversity combining, in which
signals broadcast from different transmitters are received and
combined by a terminal in its receiver front end 410. Such
operation is common in mobile telephone systems, and would need
broadcast content synchronization between base stations so that a
terminal is able to decode and combine multiple received signals.
With synchronized transmissions on TCHs with a frequency-reuse
factor of 1, macro diversity can be achieved since an equalizer in
the terminal's receiver 410 can combine the different cell's
signals. With macro diversity, the coverage is improved as well as
the bit rate at cell borders.
[0046] Broadcasting TV in a GSM/EDGE communication system as
described here would typically use unencrypted transmission with
unacknowledged-mode radio link control (RLC). Unencrypted
transmission is supported in the 3GPP standard, e.g., 3GPP TS 04.64
V8.7.0, General Packet Radio Service (GPRS); Mobile Station-Serving
GPRS Support Node (MS-SGSN) Logical Link Control (LLC) layer
specification, Rel. 99 (December 2001). If encryption is desired,
it can be performed at the application layer or be controlled by
subscription. Encrypted channels can be used for "pay" content,
such as pay-per-view events.
[0047] Ordinary GPRS channels are set up from the BM-SC 212 or
other provider of broadcast content to the base stations in the RAN
204. Content changes (within the available broadcast channels'
capacity) and quality can be managed by the BM-SC. Also, the BM-SC
can change the channel structure or timeslot tree such as that
depicted in FIG. 1 below the main-page (timeslot TS1) without
changing other parts of the network configuration.
[0048] To display real-time TV on a typical mobile phone with
acceptable quality requires a data rate of about 40 kbps with no
more than perhaps about 2% BLER. The BCCH is typically planned with
a frequency reuse factor of 12 to 15, which results in a
carrier/interference (C/I) ratio of 10 dB to 12 dB at the cell
border. The MCS-5 scheme provides 22 kbps/timeslot and around 1%
BLER at a C/I of 10 dB. It will be understood that the "packet
error rate" corresponding to a 1% BLER depends on the length of the
transmitted IP packets because the transmission is unacknowledged.
If further improved BLER is required, then error correction
techniques, such as the Forward Error Correction (FEC) (e.g., block
codes, convolutional codes, Turbo codes, and their variations),
could be used, in which case more bandwidth (about 5%-10%) would be
required. Using two BCCH timeslots for a TV channel as depicted in
FIG. 1 may provide the data rate needed for acceptable quality.
[0049] Thus, three TV channels could be served on the BCCH as
depicted by FIG. 1, with room for a channel that can be carried by
a timeslot with a 22 kbps data rate, which can be a service guide
and also information such as text news, photos, and video clips.
This channel can transmit information in a cyclic fashion, i.e.,
all information is not transmitted in each timeslot, and the mobile
can store this information for fast access. The information content
can be similar to conventional text-TV/Tele-text, or more advanced,
with multimedia content including sounds and images.
[0050] It is currently believed that typical "off-line" information
content includes more or less static text, photographs, and
recorded sound and that typical "on-line" information content
includes streaming information such as broadcast television and
radio. From one point of view, off-line content is similar to a
book or newspaper. It will be understood, however, that these
categories do not have well-defined borders. In general, however,
off-line content may be provided with coding and/or transmission
formats that are different from those used for providing on-line
content.
[0051] It is currently believed that off-line content should
include fewer errors than on-line, or streaming, content in order
to match user expectations that are based on experiences with books
and television. Accordingly, a UE should store in its memory
transmitted content that has been received and decoded without
error. To avoid having to re-transmit possibly lengthy content,
content can advantageously be divided into segments, or frames,
that are repeatedly transmitted, with each frame having a
respective error detection/correction scheme, such as FEC and/or a
cyclic redundancy check or checksum element. If a received frame
had an error that was not corrected, the UE would attempt to
receive and decode a subsequent transmission of that frame and
insert the correctly decoded frame in the memory in place of the
erroneous frame. Thus, a receiver can have many chances to detect
and correct errors in received content, including scrapping part of
the content and waiting for re-transmission. If a user chooses to
view stored content that includes one or more erroneous frames, the
erroneous frame or frames would preferably be identified as such in
a convenient way to the user.
[0052] Media broadcasting in a GSM/EDGE or similar communication
system as described here is flexible and may be extended, improved,
and enhanced in a number of ways.
[0053] For example, if spectrum is available, more TV channels may
be added by allocating the spectrum to broadcast transmission over
traffic channels. In a typical GSM communication system, frequency
reuse must be similar to current BCCH reuse to fulfill requirements
on the radio environment. The same tree-structure shown in FIG. 1
having a "TV Broadcast pointer" can be used to define additional TV
broadcast channels on TCH frequencies. In this case, the number of
timeslots needed per channel would depend on the frequency reuse,
chosen coding scheme, etc., chosen by the system operator. Coverage
and capacity would also depend on network planning.
[0054] If this application's media broadcasting is based on a
cellular-communication-system structure, it is simple to implement
different levels of "local" broadcast transmission. Depending on
demand and interest, TV channels can be broadcast in smaller or
larger parts of the cellular network, i.e., by different base
stations. It will be understood that this invention is not limited
to cellular communications systems, and in particular this
invention is not limited to GSM/GERAN systems.
[0055] Interactive or reactive add-on services, such as voting,
placing orders, etc., can be supported by the enhanced channels
described here, although a feedback channel from the terminal to
the base station would be required. Such a feedback channel can be
readily accomplished with class-A terminals that have two separate
radio transceivers, or even by modification of the existing
telecommunication standard applicable to the particular
communication system. Possibly, a terminal with two receiver chains
but only one transmitter could be used, in a manner similar to a
typical GSM/EDGE handset that has a DVB-H receiver.
[0056] A dedicated feedback channel enables user interactivity.
Information about voting, selection, buying for the application is
embedded in the broadcasted content, either in the "Program Guide"
or along with the audiovisual content. The terminal application may
store selections for later uplink transmission or, if a backchannel
is available, transmit the result back to the server. One possible
way to do this is "return SMS". For simplicity for the user,
casting a vote can be done by actuating the yes/no buttons on the
phone.
[0057] A feed-back channel can be used to order "pay-per-view"
content, and decryption keys for such content can be made available
either via the Service Guide on TS1 or on a dedicated forward
channel. If a separate forward channel is not available, a common
content decryption key can be provided in an encrypted form through
the Service Guide, and users who have paid for the requested
content can decrypt the encrypted form with user keys that they
already have. The Service Guide can be continually updated with
users who have paid and are allowed to obtain the content
decryption key.
[0058] It may also be advantageous that while a terminal is in TV
mode, i.e., being used to receive broadcast information, the digit
buttons on the terminal's keypad are used to select a TV channel.
For example, pressing "1" could mean that TV channel 1 is selected,
pressing "2" that TV channel 2 is selected, etc. A joystick or
other suitable device on the terminal could be used for volume
control or step-wise channel selection. In this way, the physical
layer is controlled from the keypad of a terminal.
[0059] For example, the UE may include keys dedicated for selection
of broadcast content. A key-press can then be interpreted such that
the physical layer in the UE (i.e., the receiver 410) should
receive and decode timeslots 4 and 5 for an arrangement such as
that depicted in FIG. 1. A block diagram of a UE 202 having such
capability is shown in FIG. 4, and a more detailed block diagram is
FIG. 5. Based on user-input information from the keypad, keyboard,
or joystick 404 and information about the broadcast system, e.g.,
the channel guide, which may be received from the network through
the receiver 410 as described above, the control processor 402
determines which timeslot(s) to receive and decode. The timeslot
information is then fed both to a front end receiver (Fe RX) 502
and a decoder 504 that are included in the receiver 410. The Fe RX
502 and decoder 504 are the "physical layer" in the UE 202. The Fe
RX 502 receives signals captured by a suitable antenna 506 and
down-converts those signals to baseband. For power conservation,
the Fe RX 502 is turned on during the timeslots corresponding to
the TV broadcast selected by the user through the keypad 404 so
that the broadcast is received and decoded.
[0060] FIG. 6 is a flow chart of a method of distributing
multimedia information that is in accordance with one of the many
aspects of this invention. In step 602, a broadcast communication
channel is divided into a plurality of timeslots. In step 604, a
pointer is included in a predetermined one of the timeslots that
points out at least one extension channel. As described above, the
one or more extension channels are included in at least one other
timeslot of the same or another broadcast communication channel and
carry unacknowledged multimedia information. In step 606, the
multimedia information is distributed by unacknowledged
transmission of the broadcast channel.
[0061] Important advantages of the broadcast techniques and systems
described here are expected to be that efficient service
provisioning is made possible and that "TV Concept" requirements,
e.g., fast switching between different TV channels, can be
fulfilled, at the same time as no new network nodes or radio
hardware are required. The broadcast solution enables efficient
delivery of TV content to multiple users in a cell. At the same
time, fast switching between channels is made possible, assuming
that all available channels are continuously
transmitted/broadcasted.
[0062] These techniques may be implemented within the existing
GSM/EDGE standard, e.g., 3GPP Rel. 5, with no or very minor impact
on existing legacy terminals; radio environment (interference) if
the TV service is transmitted over the BCCH; architecture,
signaling, etc.; and radio and core networks. For the simplest form
of TV Broadcast over GSM/EDGE, no or possibly only moderately
changed new software might be required. Assuming that necessary
hardware requirements, e.g., GSNs and EDGE-capable TRUs, are
available, no additional new equipment (in addition to terminals
having suitable TV applications) is necessary.
[0063] It is expected that this invention can be implemented in a
wide variety of environments, including for example mobile
communication devices. It will also be appreciated that procedures
described above are carried out repetitively as necessary. To
facilitate understanding, aspects of the invention are described in
terms of sequences of actions that can be performed by, for
example, elements of a programmable computer system. It will be
recognized that various actions could be performed by specialized
circuits (e.g., discrete logic gates interconnected to perform a
specialized function or application-specific integrated circuits),
by program instructions executed by one or more processors, or by a
combination of both.
[0064] Thus, the invention may be embodied in many different forms,
not all of which are described above, and all such forms are
contemplated to be within the scope of the invention. For each of
the various aspects of the invention, any such form may be referred
to as "logic configured to" perform a described action, or
alternatively as "logic that" performs a described action.
[0065] It is emphasized that the terms "comprises" and
"comprising", when used in this application, specify the presence
of stated features, integers, steps, or components and do not
preclude the presence or addition of one or more other features,
integers, steps, components, or groups thereof.
[0066] The particular embodiments described above are merely
illustrative and should not be considered restrictive in any way.
The scope of the invention is determined by the following claims,
and all variations and equivalents that fall within the range of
the claims are intended to be embraced therein.
* * * * *
References