Packet delay optimization in the uplink of a multi-hop cooperative relay-enabled wireless network
A method for communication in a wireless network is provided. The method includes a relay node receiving a data packet and determining whether to transmit the packet without performing error checking.
1. A method for communication in a wireless network, comprising:
a first network node receiving a data packet from a User Equipment (UE) measuring a channel quality measurement (CQM) based on the received packet, and
appending the CQM to the transmission of the packet to an access node, wherein the access node combines the packet received from the first network node with at least one other instance of the packet received from another node, the combination of the at least two instances of the packet being weighted by the access node based on the CQM.
2. The method of claim 1 , wherein the first network node modifies the transmission of the packet to the access node based on the CQM.
3. The method of claim 2 , wherein the first network node controls the power of the transmission of the packet to the access node based on the CQM, and wherein the packet received from the first network node and at least one other instance of the packet received from another node are at least one of:
combined at the access node; or
combined naturally over-the-air.
4. The method of claim 3 , wherein, if different frequency-time resources are used for concurrent transmission from different nodes, the power of the transmission of the packet is controlled according to the equation:
P RN − j ( i +ν)=min[ P RN _ MAX ,P 0 +10 log 10 ( M RB _ RN )+α L j +Δ TF ( i +ν)+ f ( i +ν)}
where L j is the path loss between the access node and RN-j,
Δ TF (i) is the RN-specific power adjustment controlled by the access node,
f(i) is the RN-specific closed loop power control parameter sent by the access node in the PDCCH,
P RN _ MAX is the maximum transmit power of the first network node, and
M RB _ RN represents the number of resource blocks assigned to the first network node transmission during the (i+ν) th subframe;
and wherein, if the same frequency-time resources are used for concurrent transmission from different nodes, the power of the transmission of the packet is controlled according to the equation:
P RN-j +=min{ P RN MAX ,P m −L m +L j +ψ j ( CQM )}
wherein, when the COM of the received packet is excellent, ψ j (CQM) is set to ‘0’, where the function ψj(CQM) is a monotonically increasing function with CQM, and wherein, when the CQM is low, ψ j (CQM) becomes a negative value, resulting in a reduction of transmit power, and wherein, if a UE is not part of the concurrent transmission, P m represents the transmit power of the node m that has the best CQM over the packet reception from the UE, and wherein, if a UE is part of the concurrent transmission, P m represents the transmit power of the UE.
5. The method of claim 2 , wherein, if the CQM is below a first threshold, the first network node does not send the packet, the first network node listens for another transmission of the same packet from another node or multiple nodes if the packet is not acknowledged by the access node, the first network node combines a newly received packet with the previously received packet, the first network node calculates another CQM, and the first network node compares the newly calculated CQM to the first threshold.
6. The method of claim 2 , wherein, if the CQM is not below a first threshold but is below a second threshold, the second threshold being greater than the first threshold, the first network node demodulates, decodes, re-encodes, and re-modulates the packet, and wherein, if the COM is not below the first threshold and is not below the second threshold, the first network node demodulates and re-modulates the packet but does not decode and re-encode the packet.
7. The method of claim 6 , wherein, if the first network node has not previously attempted to transmit the packet and if the transmission of the packet can occur at a scheduled subframe that is earlier than a packet transmission deadline as specified by the access node, the first network node transmits the packet as scheduled.
8. The method of claim 6 , wherein, if the first network node has previously attempted to transmit the packet or if the transmission of the packet cannot occur at a scheduled subframe that is earlier than a packet transmission deadline as specified by the access node, the first network node transmits the packet concurrently with an earliest retransmission of the same packet from a UE or with an earliest transmission of the same packet from another first network node, if the packet reception is not acknowledged by the access node.
9. The method of claim 8 , wherein the concurrent transmissions have a random transmission delay that is not more than the cyclic prefix minus the expected maximum channel dispersion if the same frequency-time resources are used for the concurrent transmissions from different nodes.
10. The method of claim 2 , wherein the CQM for the m th part of the packet is calculated during the symbol demodulation according to the equation:
c
m
=
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∑
l
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0
σ
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s
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+
m
σ
-
s
^
l
+
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σ
2
for
m
=
0
,
…
,
n
s
σ
-
1
and the overall CQM of the packet is calculated according to the equation:
c
=
n
s
∑
l
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0
n
s
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1
s
~
l
+
m
σ
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s
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where
s
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=
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(
∑
j
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J
R
-
1
W
j
R
j
)
and where represents the Fourier transform operation, W j represents the coefficients of the frequency domain equalizer for the j th receive antenna, and R j represents the received SC-OFDMA symbol over the j th receive antenna, and where {tilde over (s)} 1 =Q[s 1 ], where Q( . . . ) is the quantization function which maps the soft symbol to the M-ary QAM constellation points.
11. The method of claim 2 , wherein the CQM for the m th part of the packet, c m , is calculated during the decoding process based on log-likelihood ratios.
12. The method of claim 2 , wherein the access node sends the first network node and another node contiguous resource allocations for transmissions of the packet to the access node, each of the contiguous resource allocations having a specified starting point, and wherein the first network node and the other node use the resource allocations to transmit the packet concurrently, and wherein the contiguous resource allocations are assigned to the first network node and the other node by means of a cooperating group radio network temporary identifier.
13. A first network node in a wireless network, comprising:
a processor configured such that the first network node receives a data packet, measures a channel quality measurement (CQM) based on the received packet, and appends the CQM to the transmission of the packet to an access node, wherein the access node combines the packet received from the first network node with at least one other instance of the packet received from another node the combination of the at least two instances of the packet being weighted by the access node based on the CQM.
14. An access node in a wireless network, comprising: a processor configured such that the access node combines a data packet received from a first network node with at least one other instance of the packet received from another node, the combination of the at least two instances of the packet being weighted by the access node based on a channel quality measurement (CQM) appended to the packet by the first network node.
15. The access node of claim 14 , wherein the access node grants the nodes resources to send the packet in a first transmission, the resource grants for the first transmission being soft and being intended for transmitting data from multiple nodes, and wherein, along with the grants, the access node also specifies a time before which the packet is to be transmitted.
16. The access node of claim 14 , wherein the access node pre-defines the space time coding or the transmit delay employed across the transmit antennas of at least one cooperating first network node and at least one cooperating user equipment.
17. The access node of claim 14 , wherein the access node pre-defines the code words transmitted by at least one cooperating first network node and at least one cooperating user equipment.
18. The access node of claim 14 , wherein the access node grants the nodes resources to send the packet in a first retransmission in case of asynchronous Hybrid Automatic Repeat Request (HARQ), and wherein the access node instructs the nodes to use all the assigned resources.
19. The access node of claim 14 , wherein the access node grants the nodes resources to send the packet for a first retransmission in case of asynchronous HARQ, and wherein the resource grants for the nodes are orthogonal and contiguous.
20. The access node of claim 14 , wherein the access node sends the nodes contiguous resource allocations for transmissions of the packet to the access node, each of the contiguous resource allocations having a specified starting point, and wherein the nodes use the resource allocations to transmit the packet concurrently, and wherein the contiguous resource allocations are assigned to the nodes by means of a cooperating group radio network temporary identifier.