Patent Application
20150222393
The present invention relates to a method for providing automatic repeat request error control in a broadcast communication network, and a supporting terminal and ARQ control center for executing the method.
In order to further improve home network transmission performance an automatic repeat request mechanism, shortly called ARQ mechanism, can be applied as an error control technique in order to achieve reliable communication over an unreliable channel. Such an ARQ mechanism uses acknowledgements i.e. messages that are sent by the receiver and that are indicating that it has correctly received a packet; and timeouts which are specified periods of time allowed to elapse before an acknowledgment has to be received. If the sender receives a negative acknowledgment, shortly called NACK or does not receive an acknowledgment, shortly called ACK, before a predefined timeout, the sender usually re-transmits the packet until the sender receives an ACK or exceeds a predefined number of re-transmissions.
A schematic of such a conventional ARQ mechanism is illustrated in a broadband communication network as shown in
Such a conventional approach is suitable for broadcast communication networks such as home networks with only a few deployed terminals within one domain. In such small domains the collision problem is not a relevant issue.
However, in the event of larger broadcast communication networks collision might become a problem and the question arises of how to further improve the communication reliability in the network.
It is an object of the present invention to improve scalability and improve transmission in broadcast communication networks with a larger number of terminals.
According to an aspect of the present invention, there is provided a method for providing automatic repeat request error control in a broadcast communication network, the method comprising:
It is an advantage of the invention that due to the second transmission phase, as a response to the ARQ failure determination such as a negative acknowledgement NACK, the third terminal supports the first terminal within the broadcast communication network whereby a copy of the same data packet is available at the second terminal. By increasing the efficient signal-to-noise ratio level SNR, the decision reliability level for correctly detecting the data packet is improved at the second terminal. In this way further re-transmission of the same data packet is significantly reduced.
The present invention is based inter alia on the insight that the broadcast nature of the physical layer interface can be exploited to enable assistance of other terminals in the broadcast network in order to create a more efficient and reliable ARQ mechanism. Indeed, all devices within the broadcast communication network share the same broadcast channel and they are able to receive all transmitted signals. So, since all terminals in the broadcast network receive the data packet and the ARQ control messages ACK/NACK, some of the terminals can be used to assist the ARQ control mechanism in order to improve the reliability of the detection of the data packets at the receiving device.
According to an embodiment of the invention a supporting terminal for supporting a first terminal in an ARQ error control mechanism, in a broadcast communication network, is provided. Such a supporting terminal comprises a receiver for receiving a data packet being transmitted by the first terminal over the broadcast communication network towards a second terminal; and a storing means for storing a copy of the data packet; and a transmitter for transmitting, in the event of determination of an ARQ failure indication regarding the firstly transmitted data packet, the copy of the data packet during an identical time-interval as wherein the first terminal retransmits the data packet towards the second terminal. So, the supporting terminal is used in order to assist the conventional data re-transmission i.e. it is used to assist the communication with the goal of increasing the reliability of the decision regarding the reception of the data packet with an acceptable BER. The presence of other available terminals is exploited to improve the transmission efficiency.
In a further aspect of the method of the present invention the method comprises selecting by an ARQ control center during a previous step the third terminal as an ARQ supporting terminal for the first terminal based upon a quality of transmission and activity in the broadcast communication network. Indeed without any pre-selection, all terminals in the broadcast network could react upon an ARQ failure indication which would not be in favor of the load in the network. According to this embodiment some “free” i.e. not active terminals in the same broadcast network as the first terminal are pre-selected and used in order to assist the conventional data re-transmission towards the second terminal. An efficient utilization of the “free” terminals further increases the communication reliability through better signal detection by the terminal which should receive the data packet.
The pre-selection of one or more supporting terminals for a first terminal is based upon the quality of the transmission within the broadcast network. A terminal being located near by the receiving terminal can be pre-selected to support a terminal being located further away. A terminal with a good quality link towards the receiving terminal can be pre-selected to support transmission of a terminal with a bad quality link towards the receiving terminal.
The pre-selection of one or more supporting terminals for a first terminal is also based upon the availability of the terminal. A terminal with rather low activity can be selected to support an active first terminal i.s.o. selecting a terminal with already a high activity for its own actual transmission.
In an embodiment of the ARQ control center in a broadcast communication center, the ARQ control center comprises a selector agent for selecting, based upon quality of transmission and activity in the broadcast communication network, a terminal i.e. the third terminal as an ARQ supporting terminal for supporting the first terminal.
In another aspect of the invention the method further comprises a step of coordinating by means of an ARQ control center the second transmitting step for substantially simultaneous transmission of both packets i.e. the re-transmission of the data packet by the first terminal and the copy of the data packet by the third terminal.
Such a coordinating step is executed by an ARQ control center in a further aspect of the invention. The ARQ control center comprises hereby a coordinating agent for coordinating substantially simultaneous transmission of a copy of a data packet by a supporting terminal i.e. the third terminal and a retransmit of the data packet by the first terminal.
It has to be explained that it is important in the broadcast network to transmit both copies of the data packet simultaneously. The transmission of the copy of the data packet is transmitted substantially simultaneously with the source terminal i.e. the first terminal in order to provide multiple copies of the original data packet over independent paths and in order to hereby increase the decision reliability at the request transmitter. So the signal-to-noise ratio is improved at the first terminal. An additional copy of the original data is transmitted via statistically independent channels, which is equivalent to spatial diversity.
It has to be explained that an ARQ failure indication can either be determined by another device in the network which triggers hereafter the terminal(s) for (re)transmission or an ARQ failure indication can either be determined by the terminal itself based upon e.g. time-out which is a predetermined period that has been elapsed before an acknowledgement of good reception has been received.
According to this first implementation aspect a receiving terminal determines a SNR ratio for the received packet. Based upon SNR, the receiving terminal determines whether the packet is good received or not. In the event of a bad reception, an “ARQ failure indication” has been determined. Hereby a Not Acknowledge i.e. a NACK control message is transmitted to the transmitting terminal which reflects a question for (re)transmission by the transmitting first terminal and a supporting third terminal.
According to the second implementation aspect, the transmitting terminal as well as the supporting terminals needs to measure the time-out. The transmitting terminal determines the time-out in function of the time of the first transmission of the data packet and a first pre-determined period of time-out. The supporting terminals determine the time-out in function of the reception of the data packet from the first transmission and another pre-determined period of time-out. Both kind of terminals decides for themselves for a (re)transmission of the data packet. So, the “ARQ failure indication” is determined by the terminals themselves.
Now, in a further aspect of the present invention the ARQ failure indication can as well be determined by an ARQ control center by using cyclic redundancy check (CRC) control.
Indeed, according to the first implementation aspect, the SNR ratio can be forwarded to the ARQ control center whereby the ARQ control center decides whether the SNR is indeed within the acceptable range or not. Alternatively, the ARQ control center can decides the SNR based upon its own reception of the data packet due to the first transmission.
Furthermore, according to the above second implementation aspect the ARQ control center determines the time-out in function of the reception of the data packet from the first transmission and still another pre-determined period of time-out.
So, according to this further aspect of the present invention, the previous described step of “determining an ARQ failure indication” for the first transmission of the data packet is executed by the ARQ control center. Such an ARQ control center comprises hereby a determining means for determining an “ARQ failure indication” based upon a quality of transmission of the data packet being first transmitted by a first terminal towards a second terminal. The determination of the status of “ARQ failure indication” initiates thereby a transmission of a copy of the data packet by a supporting terminal such as the third terminal during an identical time-interval as wherein the first terminal retransmits the data packet towards the second terminal.
According to a further aspect of the present invention, the ARQ control center determines indeed an “ARQ failure indication” such as described above. In addition the method further comprises generating by the ARQ control center an ARQ control signal; and transmitting the ARQ control signal into the broadcast communication network. Herefor the ARQ control center comprises a generating agent for generating an ARQ control signal; and a transmitter for transmitting the ARQ control signal into the broadcast communication network. In this way, the ARQ control center triggers on behalf of the receiving terminal i.e. the second terminal the (re)-transmission of the data packet.
According to a further aspect of the present method, the method comprises implementing the broadcast communication network with a home network that comprises a plurality of domains. An inter-domain bridge is coupled between a first domain that comprises the first terminal and the third terminal; and a second domain that comprises the second terminal.
In such an implementation of a multiple-domain network i.e. an inter-domain communication network, a conventional ARQ mechanism would be installed from the source to the destination over the different domains. The network efficiency would significantly degrade since all re-transmissions must be done over different domains across the entire network. In e.g. ITU G.hn standard the home network is characterized by its different domains and their corresponding mediums such as twisted-pairs, coax and power line cables. Although, installation of an ARQ mechanism in a G.hn home network is considered to improve the transmission reliability, this may be indeed an adequate ARQ mechanism as long as the home network terminals belong to the same domain i.e. inter-domain communication without relaying and as long as the number of terminals is not large so that a possible collision problem does not escalate. In addition the network efficiency significantly degrades since the re-transmission requests and re-transmissions must be done over the different domains across the entire network for the inter-domain communication with a conventional ARQ mechanism. In the case of such a multiple-domain network i.e. inter-domain communication, application of a conventional ARQ mechanism from the source to the destination over the different domains, the network efficiency would significantly degrade since all the re-transmissions must be done over the different domains across the entire network.
A solution to the problem is brought with the method according to the present invention. According to the invention an efficient utilization of the “free” terminals within the same domain of the broadcast home network is applied in order to further increase the communication reliability through better signal detection. Furthermore, according to the present approach with the ARQ control center, the ARQ mechanism is segmented, corresponding to different domains and exploits the presence of other available terminals to improve the transmission efficiency. Indeed, due to the integration of the ARQ control center in the inter domain bridge, the ARQ control center is enabled to determine, on behalf of a second terminal in another domain, a failure indication. Furthermore, the ARQ control center also generates and transmits, on behalf of the receiving terminal in another domain, an ARQ control signal. The ARQ mechanism is segmented.
According to a final aspect of the present invention the method comprises not forwarding by the inter-domain bridge erroneous received packets from the first domain towards the second domain. Herefor the ARQ control center comprises a decision agent for deciding not to forward by the inter-domain bridge erroneous received packets from the first domain towards the second domain. Herewith the ARQ mechanism is not only segmented over the different domains, but also the overall transmission towards another domain is blocked, on behalf of a terminal in the other domain, upon reception by the inter domain bridge of a non-qualitative data packet. Badly received data packets are not further forwarded to its destination. This relieves the overall load in the complete home network.
It is to be noticed that the term ‘comprising’, used in the claims, should not be interpreted as being limitative to the means listed thereafter. Thus, the scope of the expression ‘a terminal comprising means A and B’ should not be limited to terminals consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the terminal are A and B.
Similarly, it is to be noticed that the term ‘coupled’, also used in the claims, should not be interpreted as being limitative to direct connections only. Thus, the scope of the expression ‘a terminal A coupled to a terminal B’ should not be limited to terminals or systems wherein an output of terminal A is directly connected to an input of terminal B. It means that there exists a path between an output of A and an input of B which may be a path including other terminals or means.
The above and other objects and features of the invention will become more apparent and the invention itself will be best understood by referring to the following description of an embodiment taken in conjunction with the accompanying drawings wherein:
The working of the different devices in the respective networks according to the present invention in accordance with its telecommunication environment that is shown in
The number of transmitters shown in the figures is chosen for illustrative purposes only, and does not limit the generality of the invention in any way. Operation described in relation to a given terminal may apply, mutatis mutandis, to other terminals in the network.
Referring to
According to conventional ARQ communication, an ARQ mechanism is initialized by means of control messages between the two terminals T1 and T2. This is shown with “Initiate ARQ state” in
As mentioned above,
Hereafter a first transmission of a data packet is started by a sending terminal i.e. the first terminals T1 towards a receiving terminal i.e. the second terminal T2. This is shown with TX1(DAT) i.e. a first transmission phase TX1 of the data packet DAT. The first transmission of the data packet is show by means of a striped arrow.
Hereafter an “ARQ failure indication” is determined. The determination of the “ARQ failure indication” can be implemented in different ways. A first embodiment is by means of a measurement of time-out periods either on the receiving side or on the transmitting side; and a second embodiment is by means of determination of a “bad” received packet by the receiving side. A “bad” received data packet is the reception of a data packet with a too high Signal-to-Noise ratio whereby the received data can't be acknowledged as being well received. Such a “bad” received packet is hereafter also called an “erroneous received data packet”. According to such a situation a negative acknowledgement is transmitted from the receiving side towards the transmitting side. However, in the event of a good reception, a positive acknowledgement is transmitted from the receiving side towards the transmitting side. Both control signals are shown in
Upon reception of an NACK trigger the first terminal is programmed according to a conventional ARQ mechanism to retransmit its data packet. This is shown in both Figures by means of TX2(DAT) i.e. a second transmission phase TX2 of the data packet DAT. The second transmission of the data packet is show by means of a dotted arrow.
Reference is now made to
The broadcast communication network comprises again by matter of an example three terminals T1, T2 and T3 coupled to each other.
According to an insight of the present invention, the broadcast character of the network is now exploited.
Indeed, the data packet DAT being transmitted by the first terminal T1 is also “seen” by the other terminals such as e.g. T3 in the network. This is shown by the striped arrow which extends now from the first terminal T1 towards the second terminal T2 but also up to the third terminal T3.
Even more, also ARQ control signals such as a NACK being transmitted on the broadcast network is also “seen” by the third terminal T3.
Furthermore a terminal such as T3 in the broadcast communication network is now further equipped according to the present invention to support a first terminal T1 during such an automatic repeat request error control mechanism i.e. not only the broadcast character exploited but also the signal (data and control) which are eventual not explicitly meant for terminals T3 but which are “seen” by T3 are now also handled by terminal T3.
Hereby the supporting third terminal T3 comprising:
In this way the third terminal T3 is enabled “to listen and to react” upon transmissions of data packets and ARQ control signals which might not be explicitly be meant for T3.
Indeed, the first additional action according to the present invention is the fact that T3 receives and stores a copy of a data packet DAT′ which is not explicitly meant for T3. This is shown on
It has to be explained that the original data packet DAT and the copy of the data packet DAT′ are basically comprising the same information but might slightly deviate from each other due to eventual faults which might have occurred during the first transmission of the data packet DAT.
Furthermore, T3 is enabled to react upon an “ARQ failure indication”-situation. As explained above, such an “ARQ failure indication”-situation might be determined by the terminal T3 itself such as e.g. time-out measurement; or might be signaled by means of an outside trigger such as e.g. reaction upon a NACK control signal.
Anyway, either one of the situations is sufficient for a supporting terminal T3 to transmit the copy of the data packet TX2(DAT′) during an identical time-interval as wherein the first terminal T1 retransmits its data packet TX2(DAT) towards the second terminal T2.
According to an embodiment of the present invention the method comprises selecting by an ARQ control center during a previous step the third terminal T3 as an ARQ supporting terminal for the first terminal T1 based upon a quality of transmission and activity in the broadcast communication network. As explained above, it might be disadvantage for the load of the network if all extra terminals in the network start reacting as supporting terminal for each other. The method and apparatus according to the invention therefore provide more efficient use of the network resources by carrying out a previous step of pre-selecting and assigning only particular terminals, called supporting terminals. The pre-selection of the supporting terminals is based upon the quality of transmission and activity in the broadcast communication which is also explained above. Referring to
Furthermore it has to be explained that the pre-selection might be performed by one of the terminals in the broadcast network but might as well be executed by a special dedicated ARQ Control Center. The ARQ control center is shown in
Indeed, besides the pre-selection process of assigning supporting terminals to terminals that need to transmit a data packet, the ARQ control center also performs the coordination to ensure simultaneous transmission during the second transmission phase of the original data packet and one or more copies of the data packet. This is shown in
In addition the ARQ-CC in
The ARQ-Failure state might be determined by the ARQ-CC upon e.g. reception of a time-out signal from T2; or upon its own measurement of a time-out after reception of the original data packet DAT by the ARQ-CC; or upon an erroneous reception of the data packet DAT.
Upon determination of such an ARQ(Failure)-Indication the ARQ-CC reacts by e.g. transmission of a NACK on the broadcast network.
For clarity and referring to
As explained above terminal T3 will as well react upon the ACK/NACK or ACK′/NACK′ and transmits the copy of the data packet DAT′ on the broadcast network (see dotted lines in
The generation and transmission of control signals ARQ-CTRL such as ACK′/NACK′ is shown in
The advantages of the present invention becomes especially clear when applying the present invention in a broadcast home network. This will be explained now by referring to
A broadcast communication network being a broadcast home network is shown. The home network comprises a plurality of domains: Domain 1 DOD1 and Domain 2 DOD are shown. The first domain DOD1 comprises a first terminal T1 and the third terminal T3 and the second domain DOD2, comprises the said second terminal T2. Between both shown domains DOD1 and DOD2 an inter-domain bridge IDB12 is coupled.
The skilled person will understand that any reference to a home network in the following description are strictly exemplary an not intended to limit the scope of application of the present invention to residential settings. The invention is in fact also applicable to other broadcast communication networks with one or more network segments present in an architecture similar to the one implied by G.hn, including office, industry, hospitality, and educational settings. Likewise, references to a “G.hn” network should not be construed as limiting the invention to implementations complying to that particular family of ITU-T Recommendations.
The ARQ control center ARQ-CC is by matter of example located in the inter-domain bridge IDB12. The ARQ-CC is in charge of the following functions:
The ARQ mechanism is segmented into several parts depending on the number of selected domains in the home network.
After the initialization phase between a first terminals T1-DOD1 in Domain DOD1 and a second terminal T2-DOD2 in Domain DOD2, the data packets are transmitted by both terminals to their corresponding domain masters i.e. respectively Domain Master A-DM1 and B-DM-2. In this way data packet DAT is transmitted by T1-DOD1 towards T2-DOD2: See on
Remark here that indeed all the respective terminals in Domain 1 and 2 will receive the packets from terminals T1-DOD1 and T2-DOD2, respectively.
The Domain Masters will decode the message headers and check for errors using CRC.
In the event when e.g. the Domain Master DOD1 detects errors in the data packet DAT, a notification is sent to the ARQ control center ARQ-CC while the erroneous packet from T1-DOD1 will not be forwarded to T2-DOD2.
The ARQ Control Center ARQ-CC requests, by means of a NACK (shown with ACK/NACK full line) to T1-DOD1, on behalf of T2-DOD2, to re-transmit the data packet DAT.
As a response to NACK (full line) the partner terminals i.e. the supporting terminals such as T3-DOD1 within the domain DOD1 which were pre-selected by the ARQ control center ARQ-CC, re-transmit a copy DAT′ of the data packet DAT that was broadcasted by T1-DOD1. In this way, several copies of the same packet (DAT and DAT′) are available at the Domain Master DOD1, which improves the decision reliability by increasing the efficient signal-to-noise (SNR) level for correct detection. Thus, further re-transmissions of the same packet may is significantly reduced.
So, in this way the ARQ request is send via the ARQ control center ARQ-CC only up to (from) the corresponding Domain Master i.e. DOD1 in order to avoid congestions and network throughput degradation. Thus, the demanding ARQ Control Requests ARQ-CTRL is reduced at the mac/network level and is localized within the corresponding domain to improve the efficiency.
In the event when the Domain Master DOD1 does not detect an error, then further signal processing is executed in order to recover the message from the received packet. Finally, further packet processing is done to retrieve the message.
In conclusion the inventive part of the present application is identified as exploitation of the broadcast nature of the physical layer interface in order to enable assistance of other “free” terminals e.g. T3 in order to create a more efficient and reliable ARQ mechanism. Since all terminals within a same domain receive ACK/NACK/DATA packets some of these terminals are pre-selected and used to assist the ARQ control center ARQ-CC and improve the reliability of detected data at the end terminal or the corresponding ARQ control center ARQ-CC. The supporting terminals e.g. T3 are pre-selected by the ARQ Control Center to provide the NACK-sender (T2 or ARQ-CC) with additional copies DAT′ of the original data DAT via statistically independent channels, which is equivalent to antenna/spatial diversity. Thus, the increased SNR is available. The segmentation of the ARQ control over different broadcast networks such as G.hn domains in a home network improve the efficiency over the entire network. In this case the communication terminals T1 and T2 are not (re)sending packets on end-to-end basis. The value of the present invention is the ability to enable provision of a more robust system performance and consequently, higher transmission efficiency leading to better quality of service (QoS) for home network services. Furthermore, the network re-transmissions and thus, the waiting time can be reduced as well.
A final remark is that embodiments of the present invention are described above in terms of functional blocks. From the functional description of these blocks, given above, it will be apparent for a person skilled in the art of designing electronic terminals how embodiments of these blocks can be manufactured with well-known electronic components. A detailed architecture of the contents of the functional blocks hence is not given.
While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention, as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 12306075.8 | Sep 2012 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/068142 | 9/3/2013 | WO | 00 |
