Friday, December 16, 2011

Work or Study Item List for LTE Release 11: LTE 2 Advanced ?

Evolving Random Access Channel
What Is The Next for Mobile System Design?
How Much Feedback Is Enough for MIMO?
How to Broadcast Multimedia Contents?
Interference Cancellation: A Short Overview
Location Based Services for Mobiles

From Chair's notes, there are more than 40 work or study items proposed for enhancing LTE Advanced or  both LTE-Advanced and HSPA. They will be completed by September 2012.
  1. Further Enhanced Non CA-based ICIC for LTE
  2. LTE Carrier Aggregation Enhancements
  3. Study on Coordinated Multi-Point Operation for LTE
  4. Study on Enhanced Uplink Transmission for LTE
  5. Study on further Downlink MIMO enhancements for LTE-Advanced
  6. Study on Further Enhancements to LTE TDD for DL-UL Interference Management and Traffic Adaptation
  7. Coordinated Multi-Point Operation for LTE
  8. Provision of low-cost MTC UEs based on LTE
  9. Proposed SI on LTE Coverage Enhancements
  10. Improvements to LTE Relay Backhaul
  11. Study on LTE Device to Device Discovery and Communication - Radio Aspects
  12. Network-Based Positioning Support for LTE
  13. Service continuity and location information for MBMS for LTE
  14. LTE RAN Enhancements for Diverse Data Applications
  15. Study on signaling and procedure for interference avoidance for in-device coexistence
  16. Study on HetNet mobility enhancements for LTE
  17. Study on RAN improvements for Machine-Type Communications
  18. RAN overload control for Machine-Type Communications
  19. Study Item on Further RAN Improvements for Machine-type Communications
  20. study item proposal for LTE and HSDPA Carrier Aggregation
  21. Enhancement of Minimization of Drive Tests for E-UTRAN and UTRAN
  22. Signalling and procedure for interference avoidance for in-device coexistence
  23. Study Item Proposal for Opportunistic Carrier Aggregation across 3GPP-LTE and WLAN
  24. Carrier based HetNet ICIC for LTE
  25. Study on further enhancements for HNB and HeNB
  26. LIPA Mobility and SIPTO at the Local Network RAN Completion
  27. Further Self Optimizing Networks (SON) Enhancements
  28. SI: Mobile Relay for E-UTRA
  29. Network Energy Saving for E-UTRAN
  30. UE Over the Air (Antenna) conformance testing methodology- Laptop Mounted Equipment Free Space test
  31. UE demodulation performance requirements under multiple-cell scenario for 1.28Mcps TDD
  32. Uplink Transmit Diversity for HSPA – Open Loop
  33. Non-contiguous 4C-HSDPA operation
  34. Study on Measurement of Radiated Performance for MIMO and multi-antenna reception for HSPA and LTE terminals
  35. Study on Inclusion of RF Pattern Matching Technologies as a positioning method in the E-UTRAN
  36. Relays for LTE (part 2)
  37. Enhanced performance requirement for LTE UE
  38. Electromagnetic Compatibility (EMC) Requirements for Multi-Standard Mobile Terminals and Ancillary Equipment
  39. SI: Passive InterModulation (PIM) handling for Base Stations
  40. E-UTRA medium range and MSR medium range/local area BS class requirements
  41. SI: Study of RF and EMC Requirements for Active Antenna Array System (AAS) Base Station
  42. RF Requirements for Multi-band and Multi-standard Radio (MB-MSR) Base Station
There are additional 11 work or study items for further enhancing HSPA itself.
  1. Eight carrier HSDPA
  2. Uplink Transmit Diversity for HSPA – Closed Loop
  3. Study on Uplink MIMO
  4. Study on HSDPA multipoint transmission
  5. Study item on HSPA enhancement for LCR TDD
  6. Four Branch MIMO transmission for HSDPA
  7. Uplink MIMO with 64QAM for HSUPA
  8. Further Enhancements to CELL_FACH
  9. HSDPA Multiflow Data Transmission
  10. Single Radio Voice Call Continuity from UTRAN/GERAN to E-UTRAN/HSPA
  11. SID: Introduction of Hand phantoms for UE OTA antenna testing

Saturday, December 10, 2011

Evolved Handovers: EV-DO and LTE

One key feature of any mobile communication system is to provide a mobility mechanism for mobiles to do fast and seamless switching between serving cells. There are many different handover mechanisms for achieving this goal. They include soft handover, which is mostly used for voice services, and hard handover, which is designed for data services. Hard handovers can be further classified as network-controlled handovers and mobile-based handovers. The interesting thing is if you look at the basic handover or handoff procedures I will explain in the next, you may feel a long-time debate on which entity , base stations or mobiles, should control handover or handoff.

Traditionally there is no standardized direct connection between two BTS's, even they both belong to the same BSC. Therefore, there usually are a long outage for a mobile do hard handover. For example, the default forward traffic channel MAC handover scheme of CDMA2000 EV-DO Rev. 0 usually results in 100~200ms outage. In order to minimize this outage for some delay-sensitive services, EV-DO Rev. A specially provides a new uplink channel,  DSC (Data Source Control) channel, for mobile to indicate early knowledge of its upcoming handover. When a mobile starts a handover in EV-DO Rev. A network, it sends a forward cell switch indication, a new DSC, to a target BTS for a duration of DSCLength. Meanwhile, it is still receiving data from its current serving BTS until this mobile performs a DRCCover change to the target BTS.  DRCCover is used by the mobile to specify its best serving BTS. During this moment, the queue transfer will be completed from the source BTS to the target BTS.

In LTE Release 8, things changed a little bit. A X2 connection between base stations, eNodeBs, is standardized and it is assumed to always exist as long as they belong to the same pooling area defined by a MME. The basic procedure for a LTE mobile to do handover becomes that the mobile sends Measurement Reports back to its current serving eNodeB and its serving eNodeB decides if to perform a handover and selects a target eNodeB. Source eNodeB then issues a Handover Request message to target eNodeB and passes necessary information. After target eNodeB accepts the request, it will prepare for it and acknowledge it after the preparation is done. As soon as source eNodeB receives Handover Request Acknowledge message, both a handover command and data forwarding are transmitted.

However, story doesn't stop here. Since a LTE mobile starts its handover when the radio link it sees from its serving eNodeB isn't very good, there is a possibility that it detects a radio link failure and can't successfully decode the handover command. In this case, it starts a RLF (Radio Link Failure) timer. Upon the expiration of RLF timer, the mobile searches for a good target eNodeB and tries to re-establish its connection with the target eNodeB while remain in connected state. During the period before a successful connection to eNobeB, source eNodeB will notice the changes and communicate with target eNodeBs through X2 interface to ensure the L1/L2 handover. If the re-connection failed, the mobile will switch from connected state to idle state and do a NAS recovery after that.

Wait a minute ... there is more.  Usually RLF timer is optimized to be several hundred ms. This means the delay of RLF timer based handover can be relatively long. If the mobile can send re-connection request to target eNodeB before RLF timer expires and target eNodeB can request handover from source eNodeB instead of waiting, the handover delay can be reduced accordingly. In this case, the handover sounds more like to be mobile-initiated or mobile-based.

Tuesday, November 29, 2011

USB Flash Drive Recovery or Repair Options

Someday your favorite and important USB flash drive will suddenly don't do its job. When you try to access your files in it, it may take hours to complete anything. When you try to format it, a pop-up message window will tell you "device media write protected" or "unable to complete format". Before you throw it into trash can, here are something you may try.

  1. Windows, Right Click, Format, Both normal/quick format.
  2. HDD LLF Low Level Format Tool
  3. HP USB Disk Storage Format Tool
  4. Active@KillDisk
  5. Someone said it may work after put it in a freezer for a while. Who knows.
  6. If it is a flash card, you may try to format it using a digital camera or mobile phone.

Anyway, if you succeed in repairing your USB flash drive, it may be a good idea for you not to use it for storing any critical files in the future.

Thursday, November 10, 2011

Evolved Carrier Aggregation: CDMA2000 and LTE

One advanced feature of 3GPP LTE-Advanced is carrier aggregation. It is an essential mechanism for LTE Release 10/11 to meet the peak-data rate, 1Gbps, requirement of IMT-Advanced of ITU-R. Beside this, it also helps LTE maintain backward compatibility, support symmetric/asymmetric operation modes and contiguous/non-contiguous aggregations. All these features help enable a variety of network deployment scenarios, such as hot-spot operations and flexible duplex.

Historically carrier aggregation is not something brand-new in standards.  On 3GPP2 side, the IS-2000 standard supports a multi-carrier operation, Spreading Rate 3 or 3x. Spreading 3 is used when higher data rates are desired with more bandwidth available. Spreading 3 of multi-carrier operation can make IS-2000 not only is backward compatible with its IS-95 predecessor but also satisfies the requirements set forth by IMT-2000/3G at that time. With adding additional guard band, IS-2000 can be harmonization-ready with UMTS. Since IS-2000 essentially is circuit-switch based mobile system and is optimized for delay sensitive services, especially voice service.  It assumes symmetric traffic between its uplink and downlink.  Therefore its multi-carrier extension is also symmetric and very straightforward. It can be implemented either with a single RF carrier of direct spread of 3.6864 Mcps or with three separated RF carriers of 1.2288 Mcps each. Naturally this maintains backward compatibility and can even reuse existing channel cards and many hardwares.

In 2006, 3GPP2 upgraded its CDMA2000 high rate pack data (HRPD) standard, also known as EV-DO, from Rev. A to Rev. B. One key feature of Rev. B is the multi-carrier operation supporting a bandwidth from 1.25MHz up to 20MHz bandwidth and  accordingly resulting a much higher peak data rate, 4.9xMbps downlink. This makes EV-DO not only directly competing but also compatible with UMTS. Different to IS-2000 1x RTT,  EV-DO is a packet-switch based mobile system optimized for data services.  It doesn't assume the balance between uplink and downlink. Though it can be symmetrically extended in the similar fashion as IS-2000 does and maintain nice backward compatibility, it is not optimal.

Similar to HSPA, EV-DO Rev. B supports three multi-carrier operation modes, symmetric mode, asymmetric modes and enhanced asymmetric mode. For the symmetric mode, additional mechanism, Multi-Link RLP, is introduced to help solve the MAC queue hole issue. This feature is software upgradable. In order to achieve higher efficient and flexibility, asymmetric operation mode and its enhancement are introduced with merging control overheads of difference carriers. ( Note: EV-DO Rev. B = Multi-Carrier EV-DO Rev. A + more  )

For LTE-Advanced, story can go much further.  The symmetric operation mode essentially is similar to EV-DO Rev. B and IS-2000 1XRTT except the extension of OFDMA signaling is much naturally scalable. The interesting part is on asymmetric operation mode. LTE-Advanced proposed a concept of carrier segmentation, which can also be found in the enhanced asymmetric mode of EV-DO Rev. B.  LTE carrier segment is a pool of adjacent component carriers with a total bandwidth up to 110 resource block or 20MHz while it is up to 4 forward link carriers in EV-DO Rev. B.

And ... story will never stop here.  One of the reasons is that carrier aggregation is naturally related to interference management and heterogeneous networks.  I am sure that carrier aggregation with dynamic component carrier activation/de-activation and X2 interface between eNodeBs will enable a lot of innovative applications in the future.

Monday, September 5, 2011

Install Optware on Seagate Home NAS

The Seagate GoFlex Home product line is a serial of network attached storage (NAS) devices made by Seagate for home computer network storage and backup.  As reported, it essentially is a plug computer powered by a 1.2GHz Marvell Kirkwood ARM processor 88F6281 (ARMv5te based) teamed up with 128MB of Nanya RAM and 256MB of flash memory. My Seagate GoFlex Home NAS 2TB comes with a 2TB storage space, a gigbit ethernet port and an USB 2.0 port. Inside the storage enclosure is a 3.5-inch hard disk reported to be a Seagate Barracuda ST32000542AS. The ethernet port is reported to be driven by a Marvell 88E116R LAN controller.
Figure 1. Seagate GoFlex Home Network Storage System

Before installing Optware packages on a Seagate Plug, you need decide whether you should install them on the onboard flash memory or an external storage, such as the attached NAS or an attached USB thumb drive. In my case, I chose to straightly install the packages on the NAS and mount the installation subdirectory under the root "/". Whichever way you will choose, here are some considerations.
  1. Try to conserve the limited resource on the onboard flash memory. 
  2. The external USB thumb drive should be ext2 or ext3 formatted.
The key package ipkg-opt to be installed can be download from NSLU2 repository. You can either wget it directly onto your Seagate Plug or download separatedly and upload to your installation drive.
Here are the lines for achieving this.
  • mkdir  /opt
  • cd  /home/YourUserName/GoFlex\ Home\ Personal/ 
  • mkdir opt 
  • mount  --bind /home/YourUserName/GoFlex\ Home\ Personal/   /opt
  • mount
The package is packed with gz compression so the next step is to unpacked it.
  • tar  xvzf  ipkg-opt_0.99.163-10_arm.ipk
  • tar  xvzf  data.tar.gz
  • ls  /opt/etc/ipkg.conf
If everything went well, you will end up with debian-binary, control.tar.gz and data.tar.gz from the first unpacking. Additional subdirectories, such as bin, etc, share, and lib, from the second unpacking. After the installation, it is time to do some additional configuration and tests.
  • echo  'src seagateplug-stable http://ipkg.nslu2-linux.org/feeds/optware/cs08q1armel/cross/stable' >> ipkg.conf
  • echo  'src seagateplug-unstable http://ipkg.nslu2-linux.org/feeds/optware/cs08q1armel/cross/unstable' >> ipkg.conf
  • /opt/bin/ipkg  update
Finally to make sure the package you installed works properly, you need make the following configurations.
  • ls  /etc/init.d/rcS
  • cp  rcS rcS.old
  • vi  /etc/init.d/rcS
    • insert either "mount  --bind /home/YourUserName/GoFlex\ Home\ Personal/  /opt" right before the line that says hostname
    • exit the editor.
  • vi  /etc/profile
    • on the first line, type in "#!/bin/bash".
    • on the second line, type in "export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/opt/bin:/opt/sbin". 
    • exit the editor.
  • vi  /root/.bash_profile
    • on the first line, type in "#!/bin/bash".
    • on the second line, type in "export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/opt/bin:/opt/sbin".
    • on the third line, type in "mount  --bin /home/YourUserName/GoFlex\ Home\ Personal/  /opt" 
    • exit the editor.
  • ipkg  update

Wednesday, January 5, 2011

IVR codes for Linksys/Cisco SPAxxxx or PAP2

A list for who knows what it is for.

Check DHCP 100#
Enable/Disable DHCP 101#
Check IP address 110#
Set IP address 111# (use * for period)
Check Network Mask 120#
Set Mask 121#
Check Gateway 130#
Set Gateway 131#
Check MAC 140#
Check Firmware version 150#
Check DNS 160#
Set DNS 161#
Check Web Server Port 170#
Enable/Disable Web Server 7932# (may require password)
Manual Reboot 732668#
User Factory Reset (only changes user settings) 877778#
Factory Reset (all non default settings change) 79738#