FORM 2
The Patent Act 1970
(39 of 1970)
&
The Patent Rules, 2005
COMPLETE SPECIFICATION
(SEE SECTION 10 AND RULE 13)
TITLE OF THE INVENTION
"A METHOD OF BUFFER STATUS REPORTING FOR RELAY NODES IN CELLULAR NETWORKS"
APPLICANTS:
Name Nationality Address

Indian Institute of Indian Information Networks Laboratory, Room
Technology Bombay No. 244, 2nd Floor, Dept of Electrical
Engineering, Indian Institute of
Technology Bombay, Powai, Mumbai
400076, Maharashtra, India
The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed:-

TECHNICAL FIELD
The embodiments herein relate to cellular networks and, more particularly, to a relay node based architecture in cellular networks.
BACKGROUND
Relay assisted cellular networks have been proposed which involve a communication link between a set of users and a serving Base Station (BS) via Relay Nodes (RNs). RNs assist the BS and provide an increase in coverage of the BS and/or improvement in capacity of the cellular network.
In a relay assisted cellular network, there are three links: the link between user and RN is known as access link, the link between RN and BS/RN is known as backhaul link (also known as relay link) and that between user and BS is known as direct link. The users connected to BS via RN are known as indirect users and the users directly connected to BS are known as direct users.
The data for Uplink (UL) transmission are buffered at different UEs. Conveying the amount of data buffered at UEs to the scheduler at BS helps implement queue aware UL schedulers. Buffer Status Report (BSR) has been proposed to convey the amount of data buffered at users to the scheduler located at BS.
BSR can be used to convey the amount of data buffered at

indirect users to RN on access link, RN to BS/RN on backhaul link and direct users to BS on direct link. In a relay-assisted cellular network, there may be more than one user or User Equipment (UE) connected to RN. In such a scenario, the BSR of an indirect UE is communicated to RN on access link and then to BS/RN on backhaul link (the RN may convey the message to the BS directly or to BS via another RN). Due to more than one UE being associated with RN, there are two ways in which the buffer status report can be conveyed by RN to BS/RN: one, on the individual user basis, which will require a lot of control signaling exchange and will also incur delays in the system. The other approach is to communicate the cumulative buffer status reports of all indirect users connected to a RN. The cumulative BSR of indirect users is the sum of buffer state values of all users connected to a RN and therefore, is likely to exceed the predetermined maximum BSR value of a single user. However, there is a pre-defined threshold on the value of BSR which may be reported by the RN or UE to the BS. In such cases where the value of the BSR exceeds the threshold, the RN is able to report only the threshold value to the BS. Accordingly, the BS allocates resources to the RN, which may not be sufficient to meet the needs of the UEs connected to the RN. This may lead to packet loss and may require re-transmission of packets, hereby increasing the load on the network.
It has also been suggested that an extension factor which is

based on the number of UEs connected to RN and is a function of their buffer sizes may be used. The proposed extension factor is multiplied by the BSR value. It uses a minimum of 6 bits to convey this information and this BSR does not vary with each request sent to the BS. However, these additional 6 bits constitute an overhead to the system and the multiplication will lead to an extra processing at the BS.
SUMMARY
In view of the foregoing, an embodiment herein provides a method of conveying buffer status information of all the User Equipments connected to the Base Station via the associated Relay Node.
Embodiments further disclose a method of using a reserved bit of the MAC PDU sub header to distinguish between the buffer state values below and above the predetermined threshold.
These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:
FIG. 1 illustrates a scenario in a relay-assisted cellular

network, according to embodiments as disclosed herein;
FIG. 2 illustrates a generic scenario in a relay-assisted cellular network, according to embodiments as disclosed herein;
FIG. 3 depicts an example of a MAC PDU, according to embodiments as disclosed herein;
FIG. 4 depicts a relay node in a relay-assisted cellular network, according to embodiments as disclosed herein;
FIG. 5 depicts a base station in a relay-assisted cellular network, according to embodiments as disclosed herein; and
FIGs. 6a, 6b and 6c depict flowcharts, according to embodiments as disclosed herein.
DETAILED DESCRIPTION OF EMBODIMENTS
The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples

should not be construed as limiting the scope of the embodiments herein.
The embodiments herein provide a communication system between user, RN and BS for the packet data transmission in a cellular network. Referring now to the drawings, and more particularly to FIGS. 1 through 6, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
FIG. 1 illustrates a scenario in a relay-assisted cellular network, according to embodiments as disclosed herein. The network, as depicted, comprises of a Base Station (BS) 103, at least one Relay Node (RN) 101 and at least one User Equipment (UE) 102. The BS 103 is connected to the cellular network using a suitable means. The BS 103 is also connected to at least one RN 101 and/or at least one UE 102 using a wireless connection means. Each RN 101 may be connected to zero or more UEs 102 and/or zero or more RNs 101. The RN 101 may be connected to the BS 103 directly. The RN 101 may also be connected to the BS 103 via other RNs 101. Each UE 102 and/or RN 101 sends across the buffer state information to the connected reporting RN 101. The reporting RN 101 collects the information from all connected UEs 102 and/or RNs 101 and makes a buffers status report (BSR) for the BS 103 or RN 101, whichever it is attached with. Depending on the size of the buffer size, the reporting RN 101 sets a flag, wherein the flag is an indication of whether the buffer size is less than or greater than a threshold. The BSR indicates

the amount of data required for uplink transmission corresponding to the UEs 102 and/or RNs 101 connected to the reporting RN 101 using an index, which has been mapped to a range of buffer size values. The BS 103 or RN 101, on receiving the BSR from reporting RN, checks the flag. Depending on the flag, the BS 103 or RN 101 checks the appropriate table for mapping the index to the correct range of buffer size values. Once the BS 103 obtains the buffer size, the BS 103 assigns appropriate resources to the reporting RN 101 (directly or via other RNs 101 between reporting RN 101 and BS 103), which in turn assigns resources to the UEs 102 and/or RNs 101.
FIG. 2 illustrates a generic scenario in a relay-assisted cellular network, according to embodiments as disclosed herein. The network, as depicted, comprises of a RN 101 connected to a first entity 202 and one or more second entities 201. The second entity 201 may be another RN 101 or a UE 102. The first entity 202 may be another RN 101 or the BS 103.
The first entity 202 has been considered to be a BS 103 and the second entity 201 is considered to be a UE 102 in the subsequent document, for the ease of explanation.
FIG. 3 depicts an example of a MAC PDU suggested by Third Generation Partnership Project - Long Term Evolution (3GPP-LTE) standard, according to embodiments as disclosed herein. The existing

Medium Access Control (MAC) Protocol Data Unit (PDU) comprises of a MAC header 301, zero or more MAC Service Data Units (SDUs) 302, zero or more MAC control elements 303 and optional padding bits. A MAC PDU header 301 comprises of one or more MAC PDU sub-headers 304, where each sub-header corresponds to one of the following: a MAC SDU, a MAC control element or padding. A MAC PDU sub-header 304 comprises of six header fields (R/R/E/LCID/F/L) except for the last sub-header in MAC PDU and the fixed sized MAC control elements, which comprises of only four header fields (R/R/E/LCID). R indicates reserved bits. An index of 6 bits is used in conveying the BSR. So, the value of index lies between 0 and 63. This index is a representation of the actual range of buffer size (in bytes) corresponding to the UE 102 or RN 101.
The MAC PDU, as disclosed above, is an example of a scenario in which embodiments as disclosed herein may be implemented; it may be obvious to a person of ordinary skill in the art to extend the invention to any telecommunication technology, which utilizes relay based architecture.
FIG. 4 depicts a relay node in a relay-assisted cellular network, according to embodiments as disclosed herein. The RN 101 contains a memory 402, a controller 401 and a communication interface 403. The communication interface 403 communicates all the messages between the RN 101 and the UEs 102. It also communicates with the BS

103. The controller 401 identifies message from various sources, classifies them and stores them in memory 402. The controller 401 aggregates the buffer sizes received from the UEs 102 connected to the RN 101. Depending on the size of the aggregated buffer size, the controller 401 sets a flag in one of the reserved bits of the MAC PDU, wherein the flag indicates whether the buffer size is less than or greater than a threshold. The flag is set to 1 if the size of the aggregated buffer size exceeds the threshold and is set to 0 otherwise. The controller 401 further maps the buffer size to an index, where the index is looked up in the appropriate table fetched from the memory 402 by the controller 401. If the flag is set to 0 then the mapping of buffer size to index is done using Table 1 (as depicted below) else Table 2 (as depicted below) is used for the mapping. The controller 401 further sends the MAC PDU containing the MAC PDU sub-header to the BS 103 using the communication interface 403.

Index
(Decimal
equivalent
of buffer
size field
value) Buffer Size
(BS) value (in
bytes) Index
(Decimal
equivalent
of buffer
size field
value) Buffer Size (BS) value (in bytes)
0 BS=0 32 1132150000
Table 1

BSR Index BS value (Kbytes) BSR Value Index BS value
000000 64 2006500
FIG. Table 5 depicts a base stati 2
on in a relay -assisted cellular

network, according to embodiments as disclosed herein. The BS 103 contains a memory 502, controller 501, resource allocator 503 and a communication interface 504. The communication interface 504 enables the BS 103 to communicate with the RN 101 or UE 102 and the network. The controller 501 receives the BSR from the RN 101, via the communication interface 504. The controller 501 checks the flag in the MAC PDU sub-header of the received BSR. If the flag is 0, then the controller fetches Table 1 from the memory 502. The controller 501 maps the index value present in the BSR to the appropriate range of buffer sizes in the Table 1. If the flag is 1, then the controller fetches Table 2 from the memory 502.
The controller 501 maps the index value present in the BSR to the appropriate range of buffer sizes in the Table 2. The controller 501, depending on the range of buffer sizes instructs the resource allocator 503 to allocate the corresponding resources to the RN 101.
FIGs. 6a, 6b and 6c depict flowcharts, according to embodiments as disclosed herein. Each RN 101 receives (601) buffer status information from UEs 102 connected to the RN 101. In case of relay assisted cellular networks, each RN 101 serves multiple UEs 102 connected to the RN 101 (termed as indirect UEs). Therefore, the RN 101 will have data corresponding to a plurality of indirect UEs 102. Let Nl be the number of indirect UEs 102 associated with the RN 101. Also, Buffer RN and

Buffer_i,x be the amount of data buffered at the RN 101 and indirect UE 'x' where x D {1, 2, ..., Nl}. Let BSR_RN be the BSR index
corresponding to the Buffer_RN which can be conveyed to the BS 103 via the backhaul link. BSR_i,x is the BSR index of the indirect UE V corresponding to Buffer_i,x which can be communicated to its RN over access link. When BSR_i,x is received at the RN 101, the RN 101 will have information about the buffer status corresponding to indirect UE 'x'. The RN 101 then checks (602) if buffer status information from more than one UE 102 is received. If buffer status information is received from more than one UE 102, then RN 101 aggregates (603) the buffer information. When BSR_i,x is available at RN, it can re-map this index to actual buffer size (Table 1) for each indirect user 'x'. Since a BSR index represents a range of buffer size, we take the mid-value of the range during re-mapping of BSR index to the actual buffer size. Let the re-mapped buffer size of an indirect user 'x' corresponding to BSR_i,x be Buffer_emap_i,x, Then the total data buffered at all indirect UEs associated with the RN 101 is computed as:
Let BSRcum be the BSR index corresponding to buffer value Buffer_cum. Also, Buffer_total = Buffer_cum + Buffer_RN is the sum of buffer value of RN 101 and all indirect UEs 102 associated with RN

101. And, BSRtotal is the BSR index corresponding to Buffertotal. We
consider both half and full duplex RN 101 to illustrate the buffer reporting
of indirect UEs. In case of in-band relaying where, access link (link
between UE 102 and RN 101) and backhaul link (link between RN 101 and
BS 103) operate on the same frequency, the wireless links must be time
division multiplexed. Therefore, a RN 101 can either transmit or receive
during a scheduling interval. We use the term half duplex or one-way RN
for these this kinds of relay nodes. Hence, BSR reported from RN 101 to
BS 103 represents either the cumulative buffer length of all indirect UEs
associated with RN 101 (i.e. Buffer_cum) or the buffer length of RN 101
(Buffer_RN). Also, in case of out-band relaying, the wireless links operate
on different frequencies. Therefore, RN 101 can transmit and receive at the
same time. We use the term full duplex RN for these this kinds of relay
nodes. In such cases, BSR transmitted by RN 101 to BS 103 (i.e.
BSRtotal) over backhaul link represents the sum of buffers of all indirect
UEs and buffer of RN (i.e. BufferJotal). Hence, the RN 101 checks (604)
if it wants to add its buffer information to the cumulative buffer value of
indirect users associated with it. If yes, then RN 101 adds (605) these
buffer values. The controller 401 of the RN 101 then checks (606) if the
aggregated buffer value (can be Buffercum or Buffer_RN or Buffertotal)
> threshold. If the aggregated buffer value is less than threshold, then RN
101 sets (607) flag = 0 in the sub-header of MAC PDU. If the buffer

aggregated value is greater than threshold, then the RN 101 sets (608) flag = 1 in the sub-header of MAC PDU. The MAC PDU contains the BSR value which is an index corresponding to the aggregate buffer size. The index has been selected by mapping the aggregate buffer size to the corresponding index in the corresponding table (which depends on the aggregated buffer size; Table 1 if the buffer size is less than the threshold and Table 2 if the buffer size is greater than the threshold). The RN 101 then sends (609) the MAC PDU to the BS 103.
The BS 103 checks (610) the flag of the MAC PDU subheader. If the flag=0 (611) then, the BS 103 checks (613) Table 1 stored in the memory to map the BSR indices into actual buffer sizes. In case the flag =1 and not 0 (611) the BS 103 checks (612) Table 2 stored in the memory to map the BSR indices into actual buffer sizes. The BS 103 finally assigns (614) resources to the requesting RN 101 and sends (615) the resource allocation information to the RN 101 based on received buffer values. The various actions in method 600 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed in FIGs. 6a, 6b and 6c may be omitted.
The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the network elements. The network elements shown in Figs. 1, 2, 4 and 5

include blocks, which can be at least one of a hardware device, or a combination of hardware device and software module.
The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the claims as described herein.

WE CLAIM
What is claimed is: 1. A method for enabling a Relay Node (RN) to send a Buffer Status Report (BSR) to a first entity in a communication network, wherein said RN is connected to at least one second entity and said RN is further connected to said first entity, said method comprising of
Checking by said RN if an aggregated buffer value mentioned in said BSR exceeds a predetermined threshold;
Setting a flag in Medium Access Control (MAC) Protocol Data Unit (PDU), depending on check made by said RN of said aggregated buffer value, wherein said MAC PDU comprises of said BSR;
Sending said MAC PDU by said RN to said first entity;
Checking by said first entity of said flag in said MAC PDU;
Checking by said first entity for buffer size corresponding to said BSR in a first table or a second table, depending on said flag; and
Allocating assigned resources by said first entity to said RN, depending on said BSR.
2. The method, as claimed in claim 1, wherein said first entity is at least one of
A Base Station (BS);
A half-duplex RN; or
A full-duplex RN.

3. The method, as claimed in claim 1, wherein said second entity is at
least one of
A User Equipment (UE); A half-duplex RN; or A full-duplex RN.
4. The method, as claimed in claim 1, wherein said aggregated buffer
value further comprises at least one of
Sum of buffer values received by said RN from said at least one second
entity;
Buffer value of said RN for transmitting data to said first entity; and Summation of sum of buffer values received by said RN from said at
least one second entity and buffer values of said RN for transmitting data to
said first entity.
5. The method, as claimed in claim 1, wherein said flag is at least one of
a reserved bit in said sub-header of said MAC PDU;
an unused bit in said MAC PDU.
6. The method, as claimed in claim 5, wherein said value of said reserved bit is set to 0 by said RN, if said aggregated buffer value is less than said predetermined threshold.
7. The method, as claimed in claim 5, wherein said value of said reserved bit is set to 1 by said RN, if said aggregated buffer value is greater than said predetermined threshold.

8. The method, as claimed in claims 1 and 5, wherein checking said first table by said first entity, if said reserved bit is 0.
9. The method, as claimed in claims 1 and 5, wherein checking said second table by said first entity, if said reserved bit is 1.
10. The method, as claimed in claim 1, wherein said RN is at least one of
A half-duplex RN; or
A full-duplex RN.
11. A communication network, said communication network comprising of
a Relay Node (RN) connected to at least one second entity and said RN
further connected to a first entity, further said RN sending a Buffer Status
Report (BSR) to said first entity, said network comprising of
said RN comprising at least one means configured for
Checking if an aggregated buffer value mentioned in said BSR exceeds a predetermined threshold;
Setting a flag in Medium Access Control (MAC) Protocol Data Unit (PDU), depending on check made of said aggregated buffer value, wherein said MAC PDU comprises of said BSR;
Sending said MAC PDU to said first entity; and Said first entity comprising at least one means configured for
Checking of said flag in said MAC PDU;
Checking for buffer size corresponding to said BSR in a first table or a second table, depending on said flag; and

Allocating assigned resources to said RN, depending on said BSR.
12. The network, as claimed in claim 11, wherein said first entity is at least
one of
A Base Station (BS); A half-duplex RN; or A full-duplex RN.
13. The network, as claimed in claim 11, wherein said second entity is at
least one of
A User Equipment (UE); A half-duplex RN; or A full-duplex RN.
14. The network, as claimed in claim 11, wherein said RN is configured for
considering said aggregated buffer value further as comprising of at least
one of
Sum of buffer values received by said RN from said at least one second
entity;
Buffer value of said RN for transmitting data to said first entity; and Summation of sum of buffer values received by said RN from said at
least one second entity and buffer values of said RN for transmitting data to
said first entity.
15. The network, as claimed in claim 11, wherein said RN is configured for
setting at least one of

a reserved bit in said sub-header of said MAC PDU; an unused bit in said MAC PDU, as said flag.
16. The network, as claimed in claim 15, wherein said RN is configured for setting said value of said reserved bit to 0 by said RN, if said aggregated buffer value is less than said predetermined threshold.
17. The network, as claimed in claim 15, wherein said RN is configured for setting said value of said reserved bit to 1 by said RN, if said aggregated buffer value is greater than said predetermined threshold.
18. The network, as claimed in claims 11 and 15, wherein said first entity is configured for checking said first table, if said reserved bit is 0.
19. The network, as claimed in claims 11 and 15, wherein said first entity is configured for checking said second table, if said reserved bit is 1.
20. The network, as claimed in claim 11, wherein said RN is at least one of
A half-duplex RN; or
A full-duplex RN.
21. A Relay Node (RN) in a communication network, wherein said Relay
Node (RN) is connected to at least one second entity and said RN further
connected to a first entity, further said RN sending a Buffer Status Report
(BSR) to said first entity, said RN comprising at least one means
configured for
Checking if an aggregated buffer value mentioned in said BSR exceeds

a predetermined threshold;
Setting a flag in Medium Access Control (MAC) Protocol Data Unit (PDU), depending on check made of said aggregated buffer value, wherein said MAC PDU comprises of said BSR; and
Sending said MAC PDU to said first entity.
22. The RN, as claimed in claim 21, wherein said RN is configured for
considering said aggregated buffer value as comprising of at least one of
Sum of buffer values received by said RN from said at least one second
entity;
Buffer value of said RN for transmitting data to said first entity; and Summation of sum of buffer values received by said RN from said at
least one second entity and buffer values of said RN for transmitting data to
said first entity.
23. The RN, as claimed in claim 21, wherein said RN is configured for
setting at least one of
a reserved bit in said sub-header of said MAC PDU; an unused bit in said MAC PDU, as said flag.
24. The RN, as claimed in claim 23, wherein said RN is configured for setting said value of said reserved bit to 0 by said RN, if said aggregated buffer value is less than said predetermined threshold.
25. The RN, as claimed in claim 23, wherein said RN is configured for

setting said value of said reserved bit to 1 by said RN, if said aggregated buffer value is greater than said predetermined threshold.
26. The RN, as claimed in claim 21, wherein said RN is at least one of
A half-duplex RN; or
A full-duplex RN.
27. A first entity in a communication network, said first entity connected to
at least one Relay Node (RN), said first entity comprising at least one
means configured for Checking of a flag in a Medium Access Control
(MAC) Protocol Data Unit (PDU) received from at least one RN;
Checking for buffer size corresponding to said BSR in a first table or a second table, depending on said flag; and
Allocating assigned resources to said at least one RN, depending on said BSR.
28. The first entity, as claimed in claim 27, wherein said first entity is at
least one of
A Base Station (BS); A half-duplex RN; or A full-duplex RN.
29. The first entity, as claimed in claim 27, wherein said first entity for
checking said flag in said MAC PDU, wherein said flag is at least one of
a reserved bit in said sub-header of said MAC PDU; an unused bit in said MAC PDU.

30. The first entity, as claimed in claims 27 and 30, wherein said first entity is configured for checking a first table, if said reserved bit is 0.
31. The first entity, as claimed in claims 27 and 30, wherein said first entity is configured for checking a second table, if said reserved bit is 1.