Single Hop Count

In those experiments below, every RN is just one hop away from DN, so data packets can be sent to DN directly from each RN in MANET (Figure 6.2.2.1.1-1).

Node 7 is a DN, and the red circle represents its transmission range. So, every RN is within the transmission range of DN.

Figure 6.2.2.1.1-1: simulation topology 1

In the first experiment suite, no RN provides additional GPRS channel bandwidth to help the DN download its requested file. Thus, the packets carrying the file’s content are transmitted on the DN’s own GRPS channel. Figure 6.2.2.1.1-2 shows that the average throughput without applying out scheme is about 3.7 KB/sec.

For each average throughput data point, the point above it is the average plus the standard deviation and the point below it is the average minus the standard deviation.

In this experiment suite, TCP triggered Fast Retransmission about 38 times.

GPRS TCP Throughput

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GPRS TCP throughput +stddev -stddev

Figure 6.2.2.1.1-2: GPRS TCP Throughput

In the second experiment suite, one RN is used and its channel and the DN’s channel are used to download the file in parallel. Figure 6.2.2.1.1-3 shows that the average throughput is about 7.335 KB/sec. The throughput speedup is 1.98 (7.335 / 3.7). In this experiment suite, TCP triggered Fast Retransmission about 0~7 times, so TCP is well protected in our data transfer protocol.

In the third experiment suite, two RNs are used and in total three GPRS channels are used to download the file in parallel. Figure 6.2.2.1.1-4 shows that the average throughput is about 10.83 KB/sec. The throughput speedup is 2.92 (10.83/3.7).

In the fourth experiment suite, three RNs are used and in total four GPRS channels are used to download the file in parallel. Figure 6.2.2.1.1-5 shows that the average throughput is about 11.825 KB/sec. The throughput speedup is 3.19 (11.825/3.7).

One Rel ay Node - One Hop

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One Relay Throughput +stddev -stddev

Figure 6.2.2.1.1-3: GPRS TCP Throughput – One Relay

Two Rel ay Nodes-One Hop

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Two Relay Node Throughput +stddev -stddev

Figure 6.2.2.1.1-4: GPRS TCP Throughput – Two Relay

Thr ee Rel ay Nodes - One Hop

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Three Relay Node Throughput +stddev -stddev

Figure 6.2.2.1.1-5: GPRS TCP Throughput – Three Relay

In the fifth experiment suite, four RNs are used and in total five GPRS channels are used to download the file in parallel. Figure 6.2.2.1.1-6 shows that the average throughput is about 13.614 KB/sec. The throughput speedup is 3.68 (13.614/3.7).

Four Rel ay Nodes - One Hop

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Four Relay Node Throughput +stddev -stddev

Figure 6.2.2.1.1-6: GPRS TCP Throughput – Four Relay

In the second to fifth experiments above, each TCP connection triggered Fast Retransmission about 0~7 times, so TCP is well protected in the experiments above.

However, the current GPRS FIFO queue size mentioned in section 6.2.1 is less than Max GPRS FIFO size all the time. So, there is no packet loss in GPRS Base Station.

This is because we queue each packet in GPRS FIFO queue when the block queue of RLC module layer in GPRS Base Station is full.

In Figure 6.2.2.1.1-7, there are three TCP traffic flows belonged to three different experiments of the fifth experiment suit. The throughput of TCP swings between 20 Kbytes/sec to 10 Kbytes/sec, because DN should reorder data packets which it received and data packets from each RN.

TCP Traf f i c Fl ow- Four Rel ay

Figure 6.2.2.1.1-7: TCP Traffic Flow – Four Relay

In the sixth experiment suite, five RNs are used and in total six GPRS channels are used to download the file in parallel. Figure 6.2.2.1.1-8 shows that the average throughput is about 14.13 KB/sec. The throughput speedup is 3.81 (14.13/3.7).

Fi ve Rel ayNodes -One Hop

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Five Relay Node Throughput +stddev -stddev

Figure 6.2.2.1.1-8: GPRS TCP Throughput – Five Relay

In Figure 6.2.2.1.1-9, there are three TCP traffic flows belonged to three different experiments of the sixth experiment suit. The throughput of TCP swings between 25

Kbytes/sec to 10 Kbytes/sec before 43 seconds. The TCP throughput of this experiment suit drops to zero and rises up again several times. This is because there are some packet losses in GPRS network, so a DN would enqueue data packets until all data packet in its reordering queue are in order. We observe that GPRS Base Station dropped some data packets after 43 seconds because the GPRS FIFO queue mentioned in section 6.2.1 is overflow. The maximum size of the GPRS FIFO queue is fixed, so the GPRS FIFO queue would be overflow more frequently when we pump more UDP packets into GPRS network per second.

TCP Traf f i c Fl ow- Fi ve Rel ay

Figure 6.2.2.1.1-9: TCP Traffic Flow – Five Relay

In the seventh experiment suite, six RNs are used and in total seven GPRS channels are used to download the file in parallel. Figure 6.2.2.1.1-10 shows that the average throughput is about 13.12 KB/sec. The throughput speedup is 3.54 (13.12/3.7) even lower than the previous experiment suite using less RNs.

In Figure 6.2.2.1.1-11, the TCP throughput of this experiment suit drops to zero and then rises up again more frequency than the previous experiment suite. The reason is that a DN waste more time to reorder data packets because there are more

packet losses than the previous experiment suite.

Six Relay Node Throughput +stddev -stddev

Figure 6.2.2.1.1-10: GPRS TCP Throughput – Six Relay

TCP Traf f i c Fl ow - Si x Rel ay

Figure 6.2.2.1.1-11: TCP Traffic Flow – Six Relay

In 6.2.2.1.1-12, we conclude the experiment results in section 6.2.2.1.1.

TCP Throughput - One Hop

No RN One RN Two RNs Three RNs Four RNs Five RNs Six RNs

Figure 6.2.2.1.1-12: TCP throughput – One Hop