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Figure 7.24: Singerjärvi and Kumpuvaara throughputs plotted against SNR
Figure 7.24 shows the smooth trend of throughput against SNR for both sites Singerjär-
vi and Kumpuvaara respectively for all the measurement routes. Singerjärvi site plot on
the left has more data points in the figure as different routes were taken for the meas-
urement. In comparison to it, the plot of Kumpuvaara is much sparse. However, both of
the plots suggest that application throughput is directly proportional with SNR. Highest
throughput seen for Singerjärvi site is about 48 Mbps at 22 dB SNR. The downlink
throughputs obtained can be compared with the theoretical downlink throughputs listed
in Table 5.2. The maximum theoretical downlink throughput for a 64-QAM modulation
with 1/1 coding rate utilizing 2x2 MIMO stream is about 76 Mbps. It is much higher
than the observed maximum downlink throughput of 48 Mbps as the path loss and
BERs associated with the noisy channel has not been accounted for in Table 5.2.
The threshold requirement of 1 Mbps at the cell edge for the operator has been marked
in the both plots. 1 Mbps DL throughput requires a cell edge SINR of -11.4 dB marked
by the vertical line for the Singerjärvi site while no such marks have been made in
Kumpuvaara plot as all the SNR values are well within the cell edge limit.
For Singerjärvi site, 6.9% samples are above the SINR limit of -11.4 dB but throughput
below 1 Mbps while similar statistics for Kumpuvaara site is at just 1.5%. This means
the UE in the Singerjärvi site is served within the operator’s requirement inside the site
coverage for approximately 93% while UE in Kumpuvaara site coverage is served with-
in the operator’s requirement for approximately 98% of time. With SINR limitation of -
11.4 dB at 1 Mbps throughput, the calculated cell radius (refer to Figure 6.1) with 10
MHz bandwidth operating at 800 MHz shows 32 km approx. while the observed cell
radius with 1 Mbps limit is 19.8 km. for Kumpuvaara and 11.6 km for Singerjärvi.
The blue and red lines mark Shannon bounds for Rayleigh and AWGN channel models
providing the theoretical throughput limit. The lines are based on Equation 5.8 with the
multiplicative effect on throughputs due to the spatial multiplexing feature of MIMO.
High throughput gain due to MIMO is due to the factors: rich scattering conditions
within a cell and UE utilizing the advantage of multipath condition. These scenarios in
MEASUREMENTS AND
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59
radio environment ensure that the each layer of spatial multiplexing under MIMO op-
eration is orthogonal with each other. [30]
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