WirelessMoves

Almost exactly a year ago I first reported on WiMAX Mobile Multihop Relay (MMR). At the time, I didn't have a lot of details of how it was supposed to work. In the meantime, however, the IEEE has published an advanced draft of the spec that answer a lot of questions. Also very helpful to get an idea of MMR is this slideset. So, here's an overview of the functionality:

Especially in rural areas, there are often little or no possibilities to backhaul high bandwidths connections via a fixed line copper or fiber links. The two possibilities are then either dedicated high bandwidth microwave connections per base station or a concept in which the base stations themselves form a mesh like network to forward traffic between base stations with no dedicated backhaul connection.

In addition to rural backhauling, forwarding traffic between wireless network nodes is also an interesting method to fill coverage holes and to improve in building coverage. At first, it might seem illogical that sending a data packet over the air interface more than once actually increases the data rate. In practice, however, transmitting the packet over two or more links with a high signal to noise ratio is better than only transmitting it once but very slowly because the signal quality is low.

The 802.16j amendment to the standard covers the following points to achieve these goals without increasing the number of base stations with expensive backhaul links:

Backwards Compatibility

MMR has been specified in a way that does not require mobile devices to be aware of relay nodes. This is important as introducing relaying would otherwise not be possible in already deployed networks.

Multi Hop Capability

The standard is designed in a way that allows a packet to traverse several hops until it reaches a base station that has a backhaul connection.

Relay Station Implementation Options

From the point of view of mobile stations, relays without a dedicated backhaul connection look like a standard base station and have their own base station ID. The specification allows two kinds of relay stations (RS). A simple RS relays everything up to a real base station, including even simple messages such as ranging requests and leaves the processing of all messages to the base station. Such simple relays are also referred to as transparent relays as all links to mobile devices via relay stations are controlled by a base station. More complex relays, referred to as non transparent relays, are able to locally manage the link to the subscriber and only forward user data packets to a base station and higher layer signaling information.

Summary

An ambitious spec! Let's see if and when we see this in practice

Today a little bit of self advertisement which might be of interest to those of you in the WiMAX business: On June 12 and 13, Chris Beardsmore of Intel, John Edwards of PicoChip and myself will host a 2 day WiMAX course at the University of Oxford’s Department of Continuing Education.

I am very proud to be part of this trio and each of us has a different angle on the technology. Chris has been working on the WiMAX business development side for many years and has a lot of information to share of how WiMAX is doing from that point of view. John is the air interface expert and will share his knowledge about the in’s and out’s from basic OFDM to MIMO. And myself, being the core and radio network guy will concentrate on the WiMAX core network, the radio network, authentication, mobility and session management and lots of things around it.

So, if I have caught your interest, head over to the course’s web site for the details. During this week, there are also a number of other wireless courses given by industry experts ranging from mobile web to the latest on HSPA and LTE. So if you have a bit more time to spend, it’s very well worth to stay a few extra days!

I am glad to have the Internet in my pocket to help in situations when the organization of others make success without pain highly unlikely. Take the follwoing scenario that happend to me recently: A theater visit is organized (note the passive in the sentence) in a city none of us have visited before. Turns out instructions concerning how to find the theater are practically worthless. People in the town are helpful but have different opinions on where the theater is ranging from ‘just aroundd the corner’ to ‘at the other end of town’. So here the Internet and navigation on my Nokia N95 comes to the rescue. Googeling for the town’s and theater’s name reveals the address and phone number of the theater immediately. Ah, the theater has three stages throughout the city. That explains the different opinions of the locals. A quick look into a local newspaper reveals the theater for the play. O.k., since Google has found the address, a quick look with Nokia Maps shows us the exacct place and guides us to the theater. How nice, how painless 🙂 Needless to say that the bus driver of the other group was one hour late since he had no one finding the details with his phone.

I use OperaMini day in and day out as my prefered browser and love the experience. Well, except for one thing, the frequent network selection dialog boxes. Some say it is an S60 feature but in my opinion this is just a big bug in the software. Anyway, Constantine from Intomobile now provided a great solution to the problem: In the S60 application manager, it is possible to define the behavior for each Java program. To get rid of the stupid dialog boxes, open the application manager, select OperaMini, select Open, and then set ‘Network Access’ to ‘Ask first time’. Afterwards, no more stupid dialog boxes. Thanks, Constantine!

The only drawback seems to be that one has to select a default access point when the setting is changed. This makes it difficult to use OperaMini over the Wifi network at home when the default access point has been set to the cellular network. Well, I guess you can’t have it all.

In an earlier post , I reported on how I am using my 3 UK SIM card in 3’s Italian network for Internet access without roaming charges. This works well in the bigger cities such as Catania, Siracusa, etc. In smaller cities on the countryside, however, coverage is a mess. Often, there are at least three GSM networks and usually also some UMTS network while outdoors. But once inside somewhere, most networks just fade away. Or even worse, your mobile shows average coverage but as soon as you try to do something, the coverage indication goes away… In my apartment for example, there is complete radio silence except for 3’s UMTS network at the window. At another place where I stay sometimes, only TIM has reasonable coverage. It almost looks like in those smaller towns they just dropped a couple of base stations and never did any proper radio planning and interference analysis. So since SIM cards are cheap and Internet access to be had for a couple of Euros, I now have a SIM card for 3, one from TIM and another one from WIND. At least one works in any place. Not ideal, but pragmatic…

I am in Italy at the moment taking a short vacation and experiencing my first ‘glimpse of data roaming as it should be’: A couple of weeks ago, I picked up a ‘3’ Prepaid SIM card in the U.K. for Internet access while being in Oxford. For 10 pounds a month, one can activate a one gigabyte data option. In addition, ‘3’ doesn’t charge extra for roaming, while using one of their SIMs in one of their other networks. So here I am in Sicily, a thousand miles away from Britain, using the UK SIM card in 3’s Italian network and it works just fine. Since the add on I activated in Oxford three weeks ago lasts for 30 days, it covers my time in Italy as well. Excellent, thanks 3, that’s how it should be! I just wished you had networks in more countries!

The constelation seems right: N-series devices becoming more mature and mobile Internet access now affordable, it’s time for the ultimate test: How will a Nokia Nseries device fare in the hands of a non-techie for more than just voice calls? I don’t have the answer yet, the ‘experiment’ has just started, but I should know soon enough. After testing the N82 in and out for a week, I finally shipped it to ‘the user’ with 4 applications preconfigured: MP3 player with 40 or so CD’s preloaded, Profimail for eMail access, picture upload to Flickr and OperMini 4.1 beta for mobile web access. In addition, the phone will be used intensively as a data modem for the PC. So let’s see how that works out. I’ll keep you posted.