Digital telecommunication system with selected combination of coding schemes and designated resources for packet transmission based on estimated transmission time

• US 6,363,425 B1
• Filed: 08/07/1998
• Issued: 03/26/2002
• Est. Priority Date: 08/08/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Nystrom, Johan, H{umlaut over (oo)}k, Mikael
• Primary Examiner(s): Follansbee, John A.
• Assistant Examiner(s): EL HADY, NABIL M
• Application Number:
  US09/130,599
• Time in Patent Office: 1,327 Days
• Field of Search: 709/201, 709/211, 709/226, 709/229, 709/102, 709/104, 709/225, 714/746, 714/748
• US Class Current: 709/226
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 1/1816 with retransmission of the same, encoded, message
• CPC Class Codes: H04L 1/1874 Buffer management
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal

Abstract

The present invention relates to a method and an arrangement for communicating packet information in a digital telecommunications system. Through the invention is selected a set of designated communication resources (ch1-chn) from an available amount of resources. Every packet (P) is forward error correction encoded into an encoded packet (P_ci), via one of at least two different coding schemes (c_i), prior to being transmitted to a receiving party, over the designated communication resources (ch1-chn). An estimated transmission time is calculated for all combinations of coding scheme (c_i) and relevant distribution (d_j) of the encoded data blocks (B₁-B_Γ), in the encoded packet (P_ci) over the set of designated communication resources (ch1-chn), and the combination (c_i,d_j) is selected, which minimises the estimated transmission time.

Claims

1. A method for communicating packet information in a digital telecommunications system, wherein a variable amount of communication resources is available for each transmission of a packet between a transmitting party and a receiving party, wherein an erroneously received packet may be selectively re-transmitted and wherein the information is forward error correction encoded via one of at least two different coding schemes (c₁-c_i+k) prior to being communicated from the transmitting party to the receiving party, comprising the steps of:

before a packet (P) is communicated, selecting a combination of a coding scheme (c_i) and a set of (n) designated communication resources (ch1-chn), at least on the basis of an estimated transmission time (T_trans, T_Γ

) for an encoded packet (P_ci), which is constituted by a calculated number (Γ

_ci) of encoded data blocks; and

communicating the information from the transmitting party to the receiving party.

2. The method according to claim 1, wherein the coding scheme (c_i) is fixed during the entire transmission of the packet (P).

3. The method according to claim 1, wherein the estimated transmission time (T_trans, T_Γ

) is calculated by taking into account an estimated total transmission delay, which is at least derived from an estimated number of data block re-transmissions during the transmission.

4. The method according to claim 3, wherein the estimated number of data block re-transmissions is calculated from an estimated transmission quality measure (Q₁-Q_N) for each of a currently available amount (N) communication resources (ch1-chN).

5. The method according to claim 4, wherein the transmission quality measure (Q₁-Q_N) is estimated from at least one of the:

results of previous transmissions of information over the currently available amount of (N) communication resources (ch1-chN)

estimated bit error rates (BER) for the currently available amount of (N) communication resources (ch1-chN), and

measured signal strengths (S_p) for the currently available amount of (N) communication resources (ch1-chN).

6. A method for communicating packet information in a digital telecommunications system, wherein a variable amount of communication resources is available for each transmission of a packet between a transmitting party and a receiving party, wherein an erroneously received packet may be selectively re-transmitted and wherein the information is forward error correction encoded via one of at least two different coding schemes (c_i-c_i+k) prior to being communicated from the transmitting party to the receiving party, such that for each packet (P), the method comprising the steps of:

determining an amount of (N) currently available communication resources (ch1-chN),

selecting a set of (n) designated communication resources (ch1-chn),

estimating a transmission time (T_trans, T_Γ

) for at least two encoded packets P_ci), each comprising one or more encoded data blocks (B₁-B_Γ

), and which is each derived from encoding the packet (P) via a particular coding scheme (c_i), for sending the respective encoded packet (P_ci) over the set of (n) designated communication resources (ch1-chn),

selecting a combination of a coding scheme (c_i) and a distribution (d_j) of encoded data blocks (B₁-B_Γ

), which represent the packet (P) encoded via the coding scheme (c_i), over the (n) designated communication resources (ch1-chn), that minimizes the estimated transmission time (T_trans, T_Γ

) for the encoded data blocks (B₁-B<sub>Γ

),</sub>

encoding the packet (P), according to the coding scheme (c_i), into an encoded packet (P_ci) comprising encoded data blocks (B₁-B_Γ

), and

transmitting the encoded data blocks (B₁-B_Γ

) over the set of (n) designated communication resources (ch1-chn) in accordance with said distribution (d_j).

7. The method according to claim 6. wherein the estimated transmission time (T_trans, T_Γ

) is calculated by taking into account an estimated total transmission delay, which is at least derived from an estimated number of data block re-transmissions during the transmission.

8. The method according to claim 7, wherein the estimated number of data block re-transmissions is calculated from an estimated transmission quality measure (Q₁-Q_N) for each of a currently available amount (N) communication resources (ch1-chN).

9. The method according to claim 8, wherein the transmission quality measure (Q₁-Q_N) is estimated from at least one of the:

results of previous transmissions of information over the currently available amount of (N) communication resources (ch1-chN),

estimated bit error rates (BER) for the currently available amount of (N) communication resources (ch1-chN), and

measured signal strengths (S_p) for the currently available amount of (N) communication resources (ch1-chN).

10. A method for communicating packet information in a digital telecommunications system, wherein a variable amount of communication resources is available for each transmission of a packet between a transmitting party and a receiving party, wherein an erroneously received packet may be selectively re-transmitted and wherein the information is forward error correction encoded via one of at least two different coding schemes (c₁-C_i+k) prior to being communicated from the transmitting party to the receiving party, such that for each packet (P), the method comprising the steps of:

determining an amount of (N) currently available communication resources (ch1-chN),

estimating a transmission quality measure (Q₁-Q_N) for each of the (N) currently available communication resources (ch1-chN),

selecting a designated set of (n) communication resources (ch1-chn) from the (N) currently available communication resources (ch1-chN),

selecting a first coding scheme (c,),

computing a number (Γ

_c1) of data blocks, that would be the result if the packet (P) was encoded via the first coding scheme c₁,

selecting a first distribution (d₁) of the encoded data blocks (B₁-B_Γ

) over the designated set of (n) communication resources (ch1-chn),

calculating an estimated transmission time (T_trans, T_Γ

) for transmitting the encoded data blocks (B₁-B_Γ

), according to the selected combination of coding scheme (c₁) and distribution (d₁),

repeating the two previous steps for possible alternative distributions (d₂, . . . , d_j+d) until all relevant distributions (d₁, d₂, . . . , d_i+d) have been applied,

selecting a coding scheme (c₂), different from the previously selected coding scheme(s) (c₁), and repeating the previous four steps for this coding scheme (c₂),

repeating the previous step until an estimated transmission time (T_trans) has been calculated for all combinations of coding scheme (c₁-C_i+k) and relevant distribution (d₁-d_j+d),

selecting a combination of a coding scheme (c_i) and a distribution (d_j) of encoded data blocks (B₁-B_Γ

), which represent the packet (P) encoded via the coding scheme (c_i), over the (n) designated communication resources (ch1-chn), that minimizes the estimated transmission time (T_trans, T_Γ

) for the encoded data blocks (B₁-B_Γ

),

encoding the packet (P), according to the coding scheme (c_i), into an encoded packet (P_ci), comprising encoded data blocks (B₁-B_Γ

), and

transmitting the encoded data blocks (B₁-B_Γ

) over the set of (n) designated communication resources (ch1-chn) in accordance with said distribution (d_j).

11. The method according to claim 10, wherein the designated set of (n) communication resources (ch1-chn) comprises at most an amount of resources, which is given by either of (i) the maximal transmission capacity at the transmitting party or (ii) the maximal reception capacity at the receiving party, whichever is lowest.

12. The method according to claim 10, wherein the designated set of (n) communication resources (ch1-chn) only comprises resources in which said transmission has a quality measure (Q₁-Q_n) higher or equal to a certain quality limit measure (Q_L).

13. The method according to claim 10, wherein the relevant distribution (d₁-d_j+d) is a distribution (d₁-d₇) in which at least as many encoded data blocks are distributed on a communication resource (ch1), having a specific estimated transmission quality measure (Q₁), as on a communication resource (ch1) having a lower (Q₂<

Q₁) estimated transmission quality measure (Q₂).

14. The method according to claim 10, wherein all (n) communication resources (ch1-ch3) in the designated set are utilised in every relevant distribution (d₅-d₇).

15. The method according to claim 10, wherein the relevant distribution (d₁-d_j+d) is an as even as possible distribution (d₇) of the encoded data blocks (B₁-B₇).

16. The method according to claim 10, wherein the estimated transmission time (T_trans, T_Γ

) is calculated by at least taking into account an estimated total transmission delay, which is derived from an estimated number of data block re-transmissions during the transmission.

17. The method according to claim 16, wherein the estimated number of data block re-transmissions is calculated from the estimated transmission quality measure (Q₁-Q_N) for each of the currently available amount (N) of communication resources (ch1-chN).

18. The method according to claim 10, wherein the estimated transmission time (T_trans) is calculated through the algorithm:

$T_{\mathrm{trans}<br><br>\text{\hspace{1em}<br><br>}}=\mathrm{\tau <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{L=1}{\overset{Y}{\sum <br><br>}}<br><br>\underset{i}{\max }<br><br>N_{i,L}+\left(Y-1\right)<br><br>\left(W_1+W_2+C\right)+W_1+C$

where;

τ

is the time for transmitting one encoded data block of the encoded blocks B₁-B_Γ

in the encoded packet,

Y is an estimated total number of transmissions demanded to transmit the entire encoded packet,

N_i,L is the number of encoded data blocks transmitted on communication resource i in the L;

th transmission,

W₁ is an expected waiting time between the last encoded data block in a transmission and reception at the transmitting party of an acknowledgement message ACK/NACK from the receiving party,

W₂ is an expected time interval between reception of a negative acknowledgement message NACK and starting re-transmission of the erroneously received block(s), and

C is an estimated time for transmitting an acknowledgement message ACK/NACK.

19. The method according to claim 10, wherein the estimated transmission time (T_Γ

) is calculated through the algorithm;

$T_{\mathrm{\Gamma <br><br>}}<br><br>\left(T_1,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},T_{\mathrm{\Gamma <br><br>}-1}\right)=\{\begin{array}{c}\frac{\mathrm{\tau <br><br>}+W_1+C+\left(1-P_1<br><br>\left(0\right)\right)<br><br>W_2}{1-\left(1-P_1<br><br>\left(0\right)\right)<br><br>P_1<br><br>\left(1\right)},\mathrm{\Gamma <br><br>}=1\\ \frac{\max <br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\mathrm{Ni}\right)<br><br>\mathrm{\tau <br><br>}+W_1+C+\left(1-P_{\mathrm{\Gamma <br><br>}}<br><br>\left(0\right)\right)<br><br>\left(W_2+\underset{k=1}{\overset{\mathrm{\Gamma <br><br>}-1}{\sum <br><br>}}<br><br>P_{\mathrm{\Gamma <br><br>}}<br><br>\left(k\right)<br><br>T_k\right)}{1-\left(1-P_{\mathrm{\Gamma <br><br>}}<br><br>\left(0\right)\right)<br><br>P_{\mathrm{\Gamma <br><br>}}<br><br>\left(\mathrm{\Gamma <br><br>}\right)},\mathrm{\Gamma <br><br>}><br><br>1\end{array}$

where;

τ

is the time for transmitting one encoded data block of the encoded blocks B₁-B_Γ

in the encoded packet,

C is the time for transmitting an acknowledgement message ACK/NACK,

W₁ is an expected waiting time between the last encoded data block in a transmission and reception at the transmitting party of an acknowledgement message ACK/NACK from the receiving party,

W₂ is an expected time interval between reception of a negative acknowledgement message NACK and starting re-transmission of the erroneously received data block(s),

Γ

is the number of encoded data blocks B₁-B_Γ

in the encoded packet,

P_Γ

(k) is an estimated probability for having z re-transmissions, given that the entire encoded packet comprises Γ

encoded data blocks B₁-B_Γ

, and

max(N_i,L) is the largest number of encoded data blocks transmitted on communication resource i in the L;

th transmission.

20. The method according to claim 10, wherein the transmission quality measure (Q₁-Q_N) is estimated from at least one of the:

results of previous transmissions of information over the currently available communication resources (ch1-chN), and

measured signal strengths (S_p) for the (N) currently available communication resources (ch1-chN).

21. An apparatus for communicating packet information in a digital telecommunications system, said apparatus comprising:

a first buffer unit for storing data blocks (b₁-b_m), which constitute one packet (P),

an encoding unit for retrieving a packet (P) from the first buffer unit and producing therefrom an encoded packet (P_ci) which comprises encoded data blocks (B₁-B_Γ

),

a computing unit for

(i) deriving quality measures (Q₁-Q_N) for each communication resource (ch1-chN) of a currently available amount of resources,

(ii) determining, from the currently available amount of resources, a designated set of communication resources (ch1-chn) for transmitting an encoded packet (P_ci),

(iii) determining relevant distributions (d₁-d_j+d) of encoded data blocks (B₁-B_Γ

) over the designated set of communication resources (ch1-chn), and

(iv) calculating estimated transmission times (T_trans), for sending an encoded packet (P_ci), according to at least two different combinations of encoding (c_i) and distribution (d_j), and

a transmitting unit for communicating an encoded packet (P_ci) to a receiving party, over at least one of the resources, comprised in the designated set of communication resources (ch1-chn), according to a distribution (d_j), which in combination with a particular encoding (c_i), give the shortest estimated transmission time (T_trans).

22. The apparatus according to claim 21, further comprising:

a logging unit for storing historical events and statistics (A, N, S_p, BER) on communication resources (chα

-chω

), serving as a basis for the quality measures (Q₁-Q_N;

) of the communication resource (chα

-chω

), and

a storage unit for holding figures representing the number of encoded data blocks in at least two different encoded versions (P_ci) of the packet (P), the quality measures (Q₁-Q_N;

) and relevant distributions (d₁-d_j+d).

23. The apparatus according to claim 21, wherein:

the encoding unit comprises a bank of at least two different coding schemes (c₁, c₂, . . . , C_i+k), and

the transmitting unit comprises a second buffer unit, for storing an encoded packet (P_ci), and a status sensing unit, for determining the status of each sent encoded data block (B₁-B_Γ

) at the receiving party.

24. The apparatus of claim 21, wherein the apparatus is integral to a base station control unit for a radio telecommunications system.

25. The apparatus of claim 21, wherein the apparatus is integral to a switching unit in a packet switched telecommunications network.