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Coughing for 4G, getting 2G... Networks' penny-pinching SECRETS REVEALED

Half-rate codecs, you say? You must be joking

Top 4G? Shockingly, the team that completed the London commuter train connectivity study we covered yesterday has reported the use of half-rate codecs among UK mobile providers.

Half-rate codecs were developed as an economy measure and their use shows penny-pinching on the part of the networks. According to the study, O2 used half-rate codecs to handle almost 28.16 per cent of all the calls engineers made during the testing.

The team which did The Register's Monopoly test also looked at mobile coverage on London commuter trains. But it's not just about coverage, quality matters too and it's information that crowdsourced data such as OpenSignal and RootMetrics cannot provide because it looks below the surface.

How bad is it?

For all the brouhaha about 4G, GWS’s engineers were on 2G with O2 for more than 60 per cent of the time while testing on commuter trains. EE, meanwhile, fell back on its 2G network two-fifths of the time (41.82 per cent) during testing, but only used half-rate codecs to decode 2.96 per cent of the test calls made. Vodafone also relied on its 2G network 40 per cent of the time during testing; it used half-rate codecs to decode 7.92 per cent of all of the calls made by GWS.

Drissa-Coulibaly,-GWS-Opera

Drissa Coulibaly, GWS operations director (right), explains mobile testing to the bartender at a Paddington station pub during the Reg's Monopoly pub crawl...

Half-rate codecs – also known as EHR or Enhanced Half Rate – are an evolution of the GSM standard from the mid 1990s. When GSM was invented as a primarily European standard, the audio was optimised for the German male voice and was expected to run at 900MHz. As GSM took the world by storm, the standards were expanded, significantly with the introduction of PCS1900 in the US. The audio codecs were improved to give Enhanced Full Rate (EFR) – which sounds significantly better – and Enhanced Half Rate, which, although it sounds worse, allows twice as many calls to be handled. As technology has progressed, we’ve seen the advent of better codecs on 3G – notably wideband AMR, which both EE and Vodafone offer.

Not that EHR is ALL bad....

EHR does have a place. It was used effectively in New York on 9/11 when the mobile networks were overwhelmed. The systems were configured so that those users – emergency services – who had the priority flag set on their SIM got some frequencies reserved for themselves to make sure their calls went through. This was done at EFR, while to handle as many ordinary customer calls as possible, the remaining frequencies were run at EHR. In a case of national emergency, the use of half-rate codes is completely justified – to use it regularly is not.

When we questioned O2 on the continued use of half-rate codecs, it pointed us at another survey that rated O2 highly and gave us the following statement: "We continue to invest £1.5m every day in our network, growing our 4G network and completely modernising our 2G and 3G networks. This work is delivering faster speeds and greater coverage across the UK, ensuring our customers have a great network experience."

Interestingly, the GWS testing found that bandwidth was better when the train was moving. The firm said 24.18 per cent of data failures occurred while they were on trains in stations, while only 20 per cent when they were on trains on open stretches of track.

However, voice calls are more likely to fail on open track than in a station (one in four of the voice "failures" GWS engineers experienced occurred when they were in a station, compared to one in three when they were on open track).

GWS found that voice and data failures are more likely to occur when a train is travelling from 0-5 mph than when it is travelling between speeds of 5 and 50mph. Failures are most likely to occur when a train is travelling above 50mph.

In your correspondent's opinion, to have regressed to the two-decades-old sound quality of EHR as a matter of course is penny-pinching of the highest order.

The team also put together a Bottom 10 of London train stations: St Pancras came bottom, which mirrors The Register’s Monopoly testing – where Pentonville was fingered as a not-spot. ®

Figure 4: Top 10 worst-connected commuter stations

Ranking (worst
to best)

Station

Average voice
& data failures

1

St. Pancras

99

2

Radlett

53

3

Kentish Town

43

4

Upminster

42

5

Elstree & Borehamwood

36

6

Hendon

33.5

7

St. Alban’s City

33

8

Cricklewood

27.5

9

Kidbrooke

27

10

Ockenden

26

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