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* Posts by DohaAndy

6 posts • joined 7 Jun 2011

Moving from permie to mercenary? Avoid a fine - listen to Ben Franklin

DohaAndy

I left the UK end of 2001 after a run in with the Inland Robbingyou on this topic. I paid up what they claimed I owed them, was easier than fighting and found work abroad where the systems are more contractor friendly.

Never regretted the decision, lots of IT/telecomms work elsewhere and in the Middle East you pretty well keep everything you earn.

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Startup claims 1W wireless charging at 10 metres

DohaAndy

erp limits

Last time I checked the erp limit at 2.4gig is +20dBm, or 100mw. You are not going to get much power at 10m or even 1m.

Even if they can raise the power above the regulatory limits they then hit the power safety limits as defined by ICNIRP which are designed to stop you cooking the user.

Whole thing looks like snake oil, even if it works it won't be legal to use in most of the world.

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Boffins flip optics to make booster-free superfast fibre

DohaAndy

Could end up as being reasonably cheap

Optical fibre muxes OADM etc are rather cheap devices, you can get them for sub $1000. If this is of the same ilk you could see them going for around the same price on about 10 years.

That makes things very interesting as the range of fibre for high speed data isn't so much limited by attenuation as the non-linear effects. You end up trading speed for distance, I wonder how wideband the device is, it would be great is is did the entire ITU grid, I suspect it will only do a few channels..

I'm not surprised it was accepted as a late submission, it is potentially really big news for those who spend their lives peering into the end of such links[1].

Andy

[1] Not literally - you end up with vision problems doing this sort of thing :-)

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Huawei, ZTE clash with US over national security

DohaAndy

So unreasonable

I wonder just how many US companies would refuse to hand over information on their overseas clients in if required by the government? There is even a law forcing them to hand over data on demand.

Then they take two Chinese companies and ask “What if you were required to hand over the data by the Chinese government?”. The question is stupid.

The reality is that Huawei and ZTE are growing rapidly and the committee members etc are being bankrolled by US companies who want to stop the competition using any way they can rather than just making better and cheaper products.

The whole thing is a farce. If they were serious about security they would set up a testing centre like BT have done with Huawei under the watchful eye of the Communications-Electronics Security Group (CESG)i which is the UK Government's National Technical Authority for Information Assurance.

Proving someone hasn't done something wrong is pointless as, by definition, there is no evidence.

andy

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Australian spectrum plan a win for carriers

DohaAndy
Linux

Public safety networks are different to commercial offerings ..

There are a lot of reasons why Public Safety networks do not use commercial GSM/3G/LTE networks most are technical, others are logistical.

Public safety networks are designed with extremely high availability requirements. The network I work on has site outages measured in seconds across the entire network and we have to account for each outage. All sites on this network have at least 8 hours battery backup and generators, I can't see many cellular operators going for that. Same goes for microwave backhaul systems which are duplicated and diverse. Cellular networks are not even close to the same reliability which costs a lot of money.

The type of traffic on a Public Safety network is completely different, its common to have over 500 subscribers on the same talkgroup (virtual channel) on a public safety system. PTT on cellular is a complete joke by comparison. Group calls outnumber individual calls by about 10 to 1 on the system I monitor.

Call setup times are different. Public safety networks generally guarantee call setup in less than 0.5 second. That fireman doesn't want to wait when he is in a burning building. Then you have dispatching centres which can join users and talkgroups on demand instantly whilst recording every word which was spoken on the network.

Then there are issues of encryption and authentication, cellular operators can do this but the costs are extremely high along with the consequent limitations on them changing their network without prior security reviews.

Public safety networks are designed to be used during civil emergency when power is off and cellular networks down. Cellular networks can sometimes be used as a backup if the public safety network is down not the other way around. Saudi Arabia

There are other reasons for not using commercial networks but I hope the list above gives an idea of some of the issues.

LTE is interesting as it is the first cellular technology which could meet public safety requirements with the appropriate applications (to be written) running on the handsets however the availability issues remain for commercial operators.

Andy

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DohaAndy
Linux

700MHz is only in the USA

Only the USA is using 700MHz for public safety LTE following a directive from the FCC in January. I'd hardly call that a worldwide standard. This frequency allocation is to be used for the next generation LTE system. I think the writer of the article needs to talk to some real world radio planners.

The only internationally standardised public safety spectrum allocation, it doesn't include the USA, is 380-400MHz which is largely used for TETRA (410-430MHz is for commercial TETRA systems). There are also TETRA systems running in 800MHz in some places. Traditional VHF/UHF FM systems normally work in 146-174MHz and 430-470MHz.

I know Public safety LTE systems will be in the 800MHz band, I'm working on the deployment one in the Middle East in Band 20 (800MHz). We are also looking for spectrum above 2GHz for urban deployment.

The big problem for public safety is the regulators are trying to flog off spectrum for as much money as they can get and public safety tends to get the leftovers. Public safety systems generally need spectrum below 1GHz because it is better for lower density deployments than higher frequencies which reduce cell sizes and allow higher traffic densities at the cost of an increased number of cell sites. The cellular operators are talking in terms of gigabits per square KM.

Andy

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