HSDPA – Page 4 – WirelessMoves

More Uses For Curbside VDSL cabinets

A couple of days ago I have rumbled a bit on the big street side cabinets that need to be put into place for VDSL every couple of hundred meters. Recently I have received an interesting eMail from one of you saying that they might just be perfect to put Wifi hotspots inside. Hm, what an interesting idea! At the size of those cabinets there should be some space left for a little access point. And backhaul is definitely not a problem with those fiber cables in the ground.

Well, why not put an HSDPA or, later on, an LTE microcell into these cabinets to increase cellular capacity in high traffic areas!? Again, no backhaul and power problem, as both are available in the cabinet. As microcells only use little transmit power and only cover small areas a little omni-directional antenna discretely put on a nearby pole or wall will do. Interesting possibilites for converged fixed/wireless network operators of the future!

Sony-Ericsson launches Tri-Band HSDPA phone

The Sony-Ericsson press announcement for the K850i is already back from July 2007 but contains a revolutionary piece of information most haven’t yet noticed:

"[…] The Sony Ericsson K850 Cyber-shot™ phone is a Tri-Band HSDPA and Quad-Band GPRS/EDGE phone […]"

Tri-Band HSDPA! This is great news since most current HSDPA phones are either only usable in the 2100 MHz band in Europe and Asia or in the 1900 MHz band in the U.S. Few if any 850 MHz mobile phones (e.g. for Australia and the U.S.) have yet been spotted. These two phones will change the game. One model produced for all parts of the world.

It’s not only great for economies of scale but also for users as it allows global High Speed Internet roaming, which is not possible today with single band HSDPA phones. People coming to Europe will be able to use their phones for high speed Internet access with prepaid SIM cards for Internet access which are available in many countries. Still waiting for the first brave operator in the U.S. doing the same thing.

P.S.: I know HSDPA data cards are also dual or tripple band today but I dream of a single device doing everything for me (and that’s certainly not a data card).

What next for mobile telephony?

… asks Moray Rumney, Lead Technologist over at Agilent in the latest edition of the Agilent Measurement Journal (3/2007). In his article, Moray takes a look at which factors contribute to the ever increasing wireless transmission speeds and explains where the limits are and why the 300+ MBit/s promised by LTE and other technologies in a 20MHz channel will remain a theoretical promise rather then becoming a practical reality. He then goes on to describe what is possible with the given physical limits and presents his thoughts about how to address capacity issues in the future. An absolute must read!

The journal is available here and the article can be found on page 32.

Light Reading Webinar on Mobile Backhaul Evolution

With mobile networks getting faster and faster a growing pain for network operators is the backhaul connection between the base station sites and the next element in the network. Today, T-1 or E-1 connections are used with a line rate of 1.5 and 2 MBit/s. With HSDPA being put in place today, backhaul capacity requirements of 3G base stations now reach 10 MBit/s or more. This means putting additional T-1 or E-1 lines in place. While this might still work today for HSDPA speeds despite the associated rising costs it certainly won’t work tomorrow for WiMAX, LTE and other Beyond 3G technologies that require backhaul capacities of 60 MBit/s per base station and more.

So the big question is what comes after T-1/E-1 connections over copper, fiber or microwave!? The common answer these days seems to be:

IP over Ethernet with the capability to carry legacy GSM (TDM) and UMTS/HSDPA (ATM) links in IP pseudo-wires alongside native IP traffic generated by native WiMAX and LTE base stations.

But how do you connect the base station sites to Carrier Ethernet Networks? Can the last mile be done over copper, is fiber required or is next generation microwave an alternative? Questions over Questions 🙂

I found some answers in a recent one hour Light Reading Webinar on the topic which is available for free at this link. If you are interested in the topic take a look.

Testing a Cat-7 HSDPA Card In a Live Network

I recently got an invitation from T-Mobile’s press center to check out T-Mobile’s HSDPA network in Friedrichshafen, which has become Deutsche Telecoms open air test bed ‘T-City’. There, the invitation said the HSDPA network was upgraded for maximum performance with category 7 HSDPA cards. In theory (no interference, no neighboring cells, single user, close to the antenna), such HSDPA cards are capable of speeds up to 7.2 MBit/s. Interesting stuff, so I went there to check it out.

In the local Telecom shop they let me check things out first hand with a notebook and an Option Globetrotter GT max HSDPA card which they said they had updated with the latest software. You won’t see a big difference when web browsing once speeds are higher than about 1 MBit/s so I decided to download a large file from a high capacity server on the Internet. The average download speed was around 4.2 MBit/s. Quite impressive even when compared to my already fast category 6 Motorola V3xx HSDPA mobile with which I have reached 2.5 MBit/s in the past.

For more on HSDPA on my blog take a look here.

Yesss – 50 Euros For One Year of Prepaid 3G Internet Access

2007 is definitely the year Prepaid Mobile Internet Access took off in Europe. In many countries especially, tourists, business travelers and most importantly local young people and students can now get affordable wireless 3G access to the Internet with prepaid SIM cards. Mobile Virtual Network Operator Yesss in Austria now takes the concept to the next level.

For 50 euros they are selling prepaid SIMs in supermarkets which come with 3GB worth of data volume to be used over ONE’s HSDPA network within 12 months. A 1GB extension afterwards, again valid for up to 12 months, costs 20 Euros. The data rate is ‘limited’ to 1 MBit/s but quite frankly that’s a limit that is not too difficult to live with.

Need an HSDPA data card with it? No problem, they’ll give you a Option 1.8 MBit/s HSDPA PCMCIA card for 39 Euros or a Huawei E220 USB modem for 149 Euros. The offer seems to be a rampant success, their online shop is currently sold out. In ‘Hofer’ supermarkets, and there seems to be one around every corner in Austria, the SIM cards are still available but they also have run short on the hardware.

Since I am in Austria every now and then I recently got myself a SIM card from one of the Hofer shops. Plug and play, no registration, nothing. Just buy the card, put it into your UMTS or HSDPA mobile/modem and off you go.

As always there is at least one catch 🙂 The SIM can only be used for Internet access, no voice or SMS allowed. As a consequence the SIM is only good for Internet access with Notebooks and other ‘non voice’ devices (Note: The SIM works fine in a mobile phone used as a modem for the notebook but voice calls are rejected). Makes sense from an operator point of view I guess. Otherwise nobody would buy pocket Internet access offers for 10 euros a month for a couple of megabytes anymore.

The other slight catch is that the ONE network used by Yesss does not have EDGE in areas where they have no 3G coverage. Therefore it’s kind of all or nothing.

For the details check out the Prepaid Wireless Internet Access Wiki.

Direct Tunnel – GPRS Core Network Streamlining

While work is ongoing on 3GPP LTE (Long Term Evolution) and SAE (System Architecture Evolution), current 3G networks continue to be enhanced as well. Since the 3G air interface is in the process continues to evolve with HSPA (High Speed Packet Access) it was felt in the standards groups that the 3G core network should be streamlined to handle the increasing network traffic more efficiently.

One part of the network in particular has been waiting for optimization for quite some time. In today’s 3G packet core architecture the SGSN (Serving GPRS Support Node) which is the gateway between the radio network and the core network handles both signaling traffic (e.g. to keep track of a users location) and the actual data packets exchanged between the user and the Internet. Since the users location can change at any time, data packets are tunneled (encapsulated) from the gateway to the Internet (The Gateway GPRS Support Node, GGSN) via the SGSN over the radio network to the mobile device. The current architecture uses a tunnel between the GGSN and the SGSN and another one between the SGSN and the Radio Network Controller (RNC). All data packets thus have to pass the SGSN which has to terminate one tunnel, extract the packet and put it into another tunnel. This requires both time and processing power.

Since both the RNC and the GGSN are IP routers this process is not really required in most circumstances. The one tunnel approach now standardized in 3GPP thus foresees that the SGSN can create a direct tunnel between the RNC and the GGSN and thus remove itself from the chain. Mobility Management remains on the SGSN, however, which means for example that it continues to be responsible to modify the tunnel in case the mobile device is moved to an area served by another RNC.

The approach does not work for international roaming since the SGSN has to be in the loop in order to count the traffic for inter-operator billing purposes. Another case where the one tunnel option can not be used is in case the SGSN is asked for example by a prepaid system to count the traffic flow. A small limitation since in practice it’s also possible to connect such a system to the GGSN (via Diameter).

For the details have a look at the following documents:

Direct Tunnel 3GPP Work Item Description SP-060142_S2-060545
The TR (Technical Recommendation) describing the overall design and impact on existing functionalities: TR 23.809
The Change Request (CR) for 3GPP TS 23.060
And the latest version of the ‘GPRS Service Description; Stage 2’ which contains the enhancements. TS 23.060 7.4.0

Verizon and LTE: All Over IP Is Shaking Up The Wireless World

Recent reports (here and here) that Verizon has chosen LTE as a successor technology of its current CDMA 1xEVDO Rev A. instead of UMB is likely to be a big blow for Qualcom and the CDMA industry as a whole. While the other big CDMA network operator Sprint has decided to go for WiMAX and a lot of global CDMA operators have already jumped ship and went to UMTS/HSDPA, Verizon is the latest addition to the list.

UMB, LTE and WiMAX are all ‘IP only’ technologies that strictly separate the wireless network from the applications running above. This is not only beneficial for users (as discussed here) but also allows network operators to jump ship when going to the next technology. Just as in the case of Verizon and Sprint. No UMTS operators have so far shown their interest to do the same, except for the threats of Vodafone that the LTE timeline is too slow for them and that they are looking what WiMAX can do for them. Might the tight integration of LTE into the already existing 2G/3G GSM/UMTS ecosystem keep operators at bay?

So while UMB is not dead yet, the hill they have to climb just got a lot steeper.

The Mobile Internet and Event Reporting in Italy

I’ve been in Rome recently and over the weekend attended one of the V-Day manifestations with a friend for more direct democracy in Italy initiated by Beppe Grillo. I mention this on my technical blog as I was very happy to see a couple of organizations reporting from the event which used a 3.5G network to broadcast their stories in real time via the Internet and radio.

The first picture on the left shows two guys of TheBlogTV interviewing people at the event. The guy on the left operates the camera while the guy on the right with the Mac (!) controls the software which sends the live video stream with the USB data card that hangs down from the notebook on the left to the Internet (recognize the Huawei logo?). I know there are already integrated mobile phone solutions available that do the same thing but this way the quality is probably better (at least for now).

The second picture shows the transmission equipment of Radiololgiata which transmits both on FM (96.6) and on the Internet. I didn’t talk to them personally as they were quite busy but I am sure the N70 connected to the equipment via the USB cable was NOT used for sending SMS messages 🙂

Great examples of how the mobile Internet revolutionizes event reporting and allows anyone to broadcast to a large audience in real time, in good quality (think HSUPA with 500+ kbit/s bandwidth) and with little cost for equipment. I modestly contributed to the reporting and uploaded some pictures to flickr in real time.

Continuous Packet Connectivity (CPC) Is Not Sexy – Part 3

In a previous post I’ve given a broad overview of a 3GPP release 7 work item called "Continuous Packet Connectivity" (CPC).
This feature or rather this set of features aim to improve user
experience by enhancing battery lifetime, reaction time after idle
times and to increase network bandwidth in situations with many
simultaneous voice over IP and other real time service users. Rather
than introducing a bold new concept, CPC very much works "under the
hood" by improving functions that are already present. Part 2 of this mini series has started to look at a first set of features and this part now finishes by looking at the remaining ones:

Discontinuous reception (DRX) in Downlink at the UE (based on section 4.5 of 3GPP TR 25.903):

While a mobile is in activate high speed (HSDPA) mode it has to monitor one or more high speed shared control channels (HS-SCCH) to see when packets are delivered to it on the high speed shared channels. This monitoring is continuous, i.e. the receiver can never be switched off.

For situations when no data is transmitted or the average data transfer rate is much lower than what could be delivered over the high speed shared channels, the base station can instruct the mobile to only listen to selected slots of the shared control channel. The slots which the mobile does not have to observe are aligned as much as possible with the uplink control channel gating (switch off) times. Thus there will be times when the terminal can power down the transmitter unit to conserve energy.

Once more data arrives from the network than what can be delivered with the selected DRX cycle the DRX mode is switched off again and the network can once again schedule data in the downlink continuously.

HS-SCCH-less operation which includes an HS-SCCH less initial transmission (based on section 4.7 and 4.8 of TR 25.903):

This feature is not intended to improve battery performance but to increase the number of simultaneous real time VoIP users in the network.

VoIP service e.g. via IMS requires relatively little bandwidth per user and thus the number of simultaneous users can be high. On the radio link, however, each connection has a certain signaling overhead. Thus, more users mean more signaling overhead which decreases overall available bandwidth for user data. In the case of HSDPA, the main signaling resources are the high speed shared control channels (HS-SCCH). The more active users, the more they proportionally require of the available bandwidth.

HS-SCCH-less operation aims at reducing this overhead. For real time users which require only limited bandwidth, the network can schedule data on high speed downlink channels without prior announcements for the terminal on a shared control channel. This is done as follows: The network instructs the mobile not only to listen to the HS-SCCH but in addition to all packets being transmitted on one of the high speed downlink shared channels. The terminal then attempts to blindly decode all packets received on that shared channel. To make blind decoding easier, packets which are not announced on a shared control channel can only have one of four transmission formats (number of data bits) and are always modulated using QPSK. These restrictions are not an issue for performance since HS-SCCH-less operation is only intended for low bandwidth real time services.

The checksum of a packet is additionally used to identify for which terminal the packet is intended for. This is done by using the terminal’s MAC address as an input parameter for the checksum algorithm in addition to the data bits. If the terminal can decode a packet correctly and if it can reconstruct the checksum the packet is intended for the terminal. If the checksum does not match then either the packet is intended for a different terminal or a transmission error has occurred. In both cases the packet is discarded.

In case of a transmission error the packet is automatically retransmitted since the terminal did not send an acknowledgement (HARQ ACK). Retransmissions are announced on the shared control channel which requires additional resources but should not happen frequently as most packets should be delivered properly on the first attempt.

And for more on HSDPA and HSUPA…

I hope that this introduction to Continuous Packet Connectivity (CPC) answers more questions than it raises. In case some fundamental things remain unclear consider taking a look at my book on mobile communication systems which covers HSDPA and HSUPA from the ground up.