Thursday 29 March 2012
Tuesday 24 January 2012
LTE Base station equipment
Saturday 14 January 2012
Next Mobile Network (NMN)
Monday 9 January 2012
Overview of LTE Handovers
From the NTT Docomo Technical journal:
The LTE handover is broadly divided into a backward handover (PS handover) and forward handover. In the former, the network performs cell switching and notifies the mobile terminal of the destination cell, and in the latter, the mobile terminal performs autonomous switching to pick up the destination cell.
To control packet loss due to a momentary cutoff at the time of radio switching, PS handover supports a data forwarding process that transfers undelivered data from the switching-source eNodeB to the switching-destination eNodeB and a reordering process that corrects sequencing mistakes between forwarded data and new data.
The forward handover can be classified into Release with Redirection triggered by a cutoff signal from the network and Non Access Stratum (NAS) Recovery in which the mobile terminal autonomously performs a NAS recovery, either of which is accompanied by data loss due to a momentary cutoff. From a different perspective, handover can be classified in the following two ways according to whether it is accompanied by Radio Access Technology (RAT) or frequency switching or by eNodeB or EPC switching (Figure 7).
1) Intra-RAT handover: This is a handover that occurs within the LTE system in which node transition occurs between sectors within an eNodeB, between eNodeBs within an EPC switch, or between EPC switches.
A handover between eNodeBs within an EPC switch may be an X2 or S1 handover. In an X2 handover, signal processing is performed by the X2 logical interface between eNodeBs, while in an S1 handover, signal processing is performed by the S1 logical interface between an eNodeB and the EPC switch. There is a tradeoff between the cost of maintaining an X2 link and the cost incurred by an S1 handover, and operations are configured accordingly.
Handover can also be classified by whether the center frequency is the same before and after handover, that is, whether the handover occurs within the same frequency or between frequencies.
2) Inter-RAT handover: This is a handover that occurs between RATs either as a transition from LTE to 3G or from 3G to LTE.
Saturday 1 October 2011
Future Mobile devices: Winners & Losers in technology
Extra-high-speed, next-generation LTE service
- Experience the first Xi-compatible tablets “docomo Tablet GALAXY Tab 10.1 LTE SC-01D” and “docomo Tablet ARROWS Tab LTE F-01D,” set for October release.
- Try out new broadband services for the high-performance Xi network, including internationally popular services and games such as Hulu and Qik Video.
Smartphone-ready device to measure acetone in breath for diet support
- The compact device measuring acetone for diet support that can easily be used anywhere and anytime.
- Visitors blow into the smartphone-connected device to measure acetone in their breath-the higher the concentration, the greater the level of hunger.
- The device also identifies when people are burning fat, based on the concentration of acetone in their breath, which rises when body fat is being burnt.
Smartphone jacket for ultra-high-speed battery charging
- This special battery jacket for smartphones achieves a full charge in just 10 minutes. A recharging indicator will show how the jacket will charge a smartphone
10~15 times faster than conventional charging devices.
Smartphone jackets for various purposes
- Three types of special jackets for smartphones that are equipped with sensors that can be customized to measure ultraviolet light and bad breath, gamma radiation and body fat.
Environmental sensor network
- Presentation of real-time atmospheric data (temperature, humidity, wind
direction/speed , precipitation, ultraviolet intensity) collected by DOCOMO’s nationwide network of approximately 2,500 environmental sensors, and a demonstration of visualizing the data using augmented reality.
The DOCOMO booth will also offer a mobile handset recycling service, where visitors can drop off old and unwanted mobile phones, rechargers, battery packs and stands. This service is open to all mobile phone users regardless of their carrier, and mobile phones will be destroyed using specialized tools to ensure the protection of personal information.
Monday 8 August 2011
Radio-over-Fiber (RoF): The existing alternative to Femtocells
Radio over Fiber (RoF) refers to a technology whereby light is modulated by a radio signal and transmitted over an optical fiber link to facilitate wireless access. Although radio transmission over fiber is used for multiple purposes, such as in cable television (CATV) networks and in satellite base stations, the term RoF is usually applied when this is done for wireless access.
In RoF systems, wireless signals are transported in optical form between a central station and a set of base stations before being radiated through the air. Each base station is adapted to communicate over a radio link with at least one user's mobile station located within the radio range of said base station.
RoF transmission systems are usually classified into two main categories (RF-over-Fiber ; IF-over-Fiber) depending on the frequency range of the radio signal to be transported.
a) In RF-over-Fiber architecture, a data-carrying RF (Radio Frequency) signal with a high frequency (usually greater than 10 GHz) is imposed on a lightwave signal before being transported over the optical link. Therefore, wireless signals are optically distributed to base stations directly at high frequencies and converted to from optical to electrical domain at the base stations before being amplified and radiated by an antenna. As a result, no frequency up/down conversion is required at the various base station, thereby resulting in simple and rather cost-effective implementation is enabled at the base stations.
b) In IF-over-Fiber architecture, an IF (Intermediate Frequency) radio signal with a lower frequency (less than 10 GHz) is used for modulating light before being transported over the optical link. Therefore, wireless signals are transported at intermediate frequency over the optical.
Access to dead zones
An important application of RoF is its use to provide wireless coverage in the area where wireless backhaul link is not possible. These zones can be areas inside a structure such as a tunnel, areas behind buildings, Mountainous places or secluded areas such a jungle.
FTTA (Fiber to the Antenna)
By using an optical connection directly to the antenna, the equipment vendor can gain several advantages like low line losses, immunity to lightening strikes/electric discharges and reduced complexity of base station by attaching light weight Optical-to-Electrical (O/E) converter directly to antenna.
Thursday 28 July 2011
Human Activity Recognition for Personalised services
Interesting article from the NTT Docomo Technical journal.
Sunday 22 May 2011
LTE World Summit 2011 - Pics and Notes from Day 1
Bart Weijermars from TMobile Netherlands said future growth will be data centric fuelled by appealing terminals, new usages, broadband and ubiquity.
Huawei has been one of the main sponsors of the event and the award and Ying Weimin spoke on how LTE is the way to more competitive Mobile Broadband.
Spectrum is the main concern though as a combination of low and high frequency will be needed. Hetnets are coming and they will be the future of the networks.
LTE is faster than expected and this is the reason there are so many operator commitments. Huawei has 40+ LTE contracts and 10 have already been launched. This is just the beginning.
Seizo Onoe from NTT Docomo spoke about Crossy. In fact during Christmas the employees were wishing each other 'Merry Crossy'. Docomo believes that the users dont care about HSPA or LTE so the Crossy is a service they are selling to the users.
Wednesday 30 March 2011
Quick Recap of MIMO in LTE and LTE-Advanced
LTE Rel. 8 also adopts rank adaptation, which adaptively controls the number of transmission layers (the rank) according to channel conditions, such as the received SINR and fading correlation between antennas (Figure 2). Each UE feeds back a Channel Quality Indicator (CQI), a Rank Indicator (RI) specifying the optimal rank, and the PMI described earlier, and the eNode B adaptively controls the number of layers transmitted to each UE based on this information.
1) Channel State Information (CSI)-RS: For CQI measurements with up-to-8 antennas, new CSI-RSs are specified in addition to cell-specific RS defined in LTE Rel. 8 for up-to-four antennas. However, in order to maintain backward compatibility with LTE Rel. 8 in LTE-Advanced, LTE Rel. 8 UE must be supported in the same band as in that for LTE-Advanced. Therefore, in LTE Advanced, interference to the PDSCH of LTE Rel. 8 UE caused by supporting CSI-RS must be minimized. To achieve this, the CSI-RS are multiplexed over a longer period compared to the cell-specific RS, once every several subframes (Figure 3). This is because the channel estimation accuracy for CQI measurement is low compared to that for demodulation, and the required accuracy can be obtained as long as the CSIRS is sent about once per feedback cycle. A further reason for this is that LTE-Advanced, which offers higher data-rate services, will be developed to complement LTE Rel. 8, and is expected to be adopted mainly in low-mobility environments.