Roaming in heterogenous access networks

Keywords: wireless networks, mobile networks, beyond 4G, femto-cells

  • Masterthesis at UNIK and KTH (Possibly also at Telenor)

News

Description (draft)

Future mobile networks have the goal of delivering more than 1 Gbit/s to users. Current 2G and 3G mobile systems have reasonable coverage both in indoor and outdoor, as data rates of typically 1-2 Mbit/s are acceptable for most customers. The International Union of Telecommunication (ITU) has stated that 4G radio systems need to provide 1 Gbit/s cell capacity for stationary users. Outdoor systems trying to provide this capacity suffer from the radio dilemma, where higher capacity typically means higher carrier frequencies and thus lower range. The second dilemma is that of attenuation from building material, typically walls and windows, which is typically around 10-20 dB for frequencies around 2.4 GHz. Thus indoor users will experience reduced bandwidth offers, and operators will experience lower cell capacity when serving indoor users. Operators aiming for full-indoor coverage need to over-dimension their network, which will reduce the total network capacity due to interference from neighbour cells.

The main task of this thesis is to establish a system level simulator, taking into considerations approximations for the technical parameters of a radio link in an outdoor to indoor coverage.

We expect that the outcome of the thesis will provide a set of simulations taking into considerations

  • a set of statistical/approximation models for radio propagation
  • a cell scenario consisting of indoor and outdoor users
  • estimated traffic scenarios, including indoor users

An estimation is expected on how much a given cell capacity is reduced given the number of users and their usage pattern.

This thesis shall provide technological arguments for a business evaluation of collaborative networks, providing indoor users through indoor networks. Examples of such indoor networks are private networks based on WLAN-type of communications or femtocells.

PC-based mobile broadband Internet connectivity using USB modem is expected to increase tenfold in next thee years (source: telecomasia.net). Mobile broadband is expected to be a higher-margin business than mobile voice for emerging markets. It is true where operators have unused capacity. While in the mature market the confidence is not so high and operators need to manage data usage. It is because the cost of managing higher data traffic escalates much faster than the revenues they generate. A technical aspect also play a role when an outdoor cell has to carry data traffic generated from indoor. Such phenomena drastically reduce the overall capacity of the cell as well. Situation aggravates when there is a high volume user (HVU) in indoor. A femtocell installed in indoor can instead carry this data trafiic. Handover to femtos can be initiated either by the outdoor cell or by the user himself.

To avoid congestions, operators are eager to offload traffic especially through WiFi. Gradually the contribution of femtocells are growing for offloading traffic.

This thesis will focus on roaming in heterogeneous networks, consisting of mobile networks mainly for outdoor coverage and indoor solutions.

A preliminary analysis suggests the use of Omnet++ for simulations, but this should be subject of a more detailed analysis.

Details of the thesis

The thesis should address the following aspects

  • Problem description
    • Establish a future communication scenario for 4G and "Beyond 4G" communication
    • Detail the scenario for high-speed indoor mobile communication, with typically >100 Mbit/s streaming quality of audio and video data
    • Simulation of outdoor-indoor problematic taking into consideration cell size, cell capacity
  • Outdoor to indoor simulation at frequencies from 900 to 2600 MHz, done by
    • Literature review for attenuation of windows and walls in buildings
    • Establish a link-level model for outdoor to indoor communication
  • Tool analysis of Omnet++
    • provide an introduction to Omnet++, with focus on high-capacity wireless links
    • implement the environment for the link layer
    • establish statistical models for loaded cells, taking into consideration increase of interference and cell-capacity reduction when a cell gets loaded with traffic
  • Simulation of traffic scenarios
    • Simulate a single cell environment with indoor usage
    • Focus is on the overall cell capacity, when indoor users require high bandwidth. Example: ITU describes 4G mobile communication as a system providing 1 Gbit/s for a stationary user.
  • Evaluation of effect of simulation parameters
  • Some ideas on business relevance
    • business aspects for mobile operators
    • femtocells and indoor radio
    • collaborative networks between outdoor and indoor
  • Conclusion

Suggested literature

Related research near to the topic

  • J. Perez-Romero, O. Sallent, R. Agusti, "Impact of Indoor Traffic on W-CDMA Capacity". look at the formulas and simulation results quite useful for us.
  • J. Perez-Romero, O. Sallent, R. Agusti, "On the Capacity Degradation in W-CDMA Uplink/Downlink Due to Indoor Traffic".
  • F. Adelantado, O. Sallent, J. Perez-Romero, R. Agusti, "Impact of Traffic Hotspots in 3G W-CDMA Networks".
  • Key Leong Thng, Boon Sain Yeo and yong Huat Chew, "Performance Study on the Effects of Cell-Breathing in WCDMA".
  • Josef Noll, Mohammad M. R. Chowdhury, "5G - Service Continuity in Heterogeneous Environments", submitted article (.pdfΔ)
  • Jörgen Grinnes, "Mobile Broadband - Todays and tomorrows expectations of customer requirements", Norwegian UMTS Forum, February 2010 (.pdfΔ)
  • J. Noll, K. Baltzersen, A. Meiling, F. Paint , K. Passoja, B. H. Pedersen, M. Pettersen, S. Svaet, F. Aanvik, G. O. Lauritzen. '3rd generation access network considerations'. selected pages from FoU R 3/99, Jan 1999 (.pdf)Δ
  • G.E. Øien, "Radio interface and access technologies for wireless and mobile systems beyond 3G", Telektronikk 3.2004, .pdfΔ

Propagation Models

Online resources

Books!

  • LTE for 4G Mobile Broadband, Air Interface Technologies and Performance, Farooq Khan Samsung Telecommunications America, Richardson, Texas, Cambridge Press.
  • LTE, The UMTS Long Term Evolution: From Theory to Practice, Stefania Sesia (Editor), Issam Toufik (Editor), Matthew Baker (Editor), WILEY.

Lingyang Song says these two books best currently the best in the market. But we may not get complete information what we are looking for from the books especially the issues of cell-breadthing.

Contacts: (please update your info at People)
Ayaz Khan Afridi, , m: +46 7393 96553
Mohammad Mushfiqur Rahman Chowdhury, , m: 9579 8902
Toan Hoang, , m: 90594880
Josef Noll, , p: 6484 4745, m: 9083 8066
Victoria Fodor; Associate Professor, Laboratory for Communication Networks, KTH, Phone: +46 8 790 4268 E-mail: vfodor@kth.se