in LTE, spectrum is divided into time-frequency axis and is called resource block (RB). For a 10 MHz BW, there are 50 RB. You can allocate as many RBs to individual users as you want.

What you are planning is possible for OFDMA...you can google for the term "scalable OFDMA".

Do I have to divide the tx power according to the number of RB? as the tx power of the bandwidth is constant if we consider it for a single cell.

yes.

You can use the following open source simulator for LTE related research:

http://www.nt.tuwien.ac.at/about-us/staff/josep-colom-ikuno/lte-simulators/

Why not ?

OFDMA means that you can split and use!! (generally)...

A very good question and the first important viewpoint is that OFDM due its Orthoganality property works beautifully for a Intracell situation where the segregation can be done in accordance with the bandwidth availability for the users. In contrast when we have a number of additonal cells like Micro,Pico , Femto etc we are limited by Intercell interference due to SINR. The problem is more pronounced when the small cells are located towards the Macro cell edge I would request you to look up a wonderful IEEE paper published in Feb'2013 of Wireless Commn which discusses the Intercell Interference problem and how to overcome the same.

yes this is possible. lTE PHY layer resources are RBs. The selection of which resource block goes to what user and under what channel and traffic conditions, is the scheduler function. ' Max SNR' scheduler base this on the highest SNR on the RB, 'Round Robin' Scheduler divides the Bandwidth fairly. 'Proportional fair' scheduler include the criteria of each user bandwidth in the equation.

check this

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&ved=0CH8QFjAI&url=http%3A%2F%2Fwww.nt.tuwien.ac.at%2Fforum%2F%3Ftx_mmforum_pi1%255Baction%255D%3Dget_attachment%26tx_mmforum_pi1%255Bfid%255D%3Datt196&ei=o8Z3UbumG6bP0QWilYGIDA&usg=AFQjCNEAwu0CnOmq1WHp3p642pjsfECqyw&sig2=2VU60pLqxgrsYFG0M9YYAg&bvm=bv.45580626,d.d2k

The answer is yes, as everyone said. However, you really need to consider the intercell interference between the macro cell and femto cell - this interference is likely occur when the user at the femto and another user at the macro are assigned at the same frequency or RB . There are several intercell interference techniques such as Soft Frequency Reuse (SFR), Fractional Frequency Reuse (FFR), and Hard Frequency Reuse. You can use any schedulers such as PF, greedy or any to choose which user will access the resources.

and a good paper to start with interference management can be found at:

http://necphy-lab.com/pub/Femtocell%20survey%20WCM-2011-105.pdf

yes, possible. Go through access technique.

first of all, what is your objective behind dividing the bandwidth in this manner ? if you go to divide and reserve a fix amount of bandwidth for each relay station type, you will loss the centralization of priority and QoS at the base station, then you have to achieve them at each relay station. moreover, bandwidth is not equally allocated among users, it should follow a scheduler that specify an amount based on QoS, service type , modulation and code rates and so on. some application needs small size with fixed period other variable period with large amount ( depend on the application).

Sure. OFDMA can be flexibly allocated either for different users and different cells according to the load i.e., user number. With this separation, orthogonality can be guaranteed accross cells to avoid inter-cell interference. However, this strict separation in frequency domain in term of resource blocks or B isn't the most efficiet for spectrum efficiency.

...but saves some serious battery life.

yes it is possible. But the interference between cells and the overhead when redistributing the bandwidth for the new number of users should be taken in consideration.