There are many companies, universities and other research institue that has been working on 5G from concept to realization. This page would give you the list of these organization and their activities.
Now a new Orgnanization has been initiated to lead specification of 5G. I would be interesting to see how the dynamics would go between 3GPP and 5G PPP about 5G Initiative.
Finally 3GPP start presenting things about 5G.
Now it seems that this consortium is becoming the leading driver for 5G at least in terms of technically defininng what 5G should be like. My guess would be that a lot of ideas from this consortium would be reflected on future 3GPP for 5G.
I strongly recommend you follow up these documents.
You can get a lot of details information from here especially possible PHY/MAC implementation including various way of Waveform creation. Go [Download] and download Deliverable Documents.
Recently (May 2013), SamSung claims that they have implemented a technology to achieve the data rate of 'tens of Gbps'. Some articles is about SamSung's claim and some other articles are from critics which dispute SamSung's claim. I don't think whether this claim is practically achievable or whether the claims are technically accurate is important. Both the claim and dispute about the claim would give you some insight on next generation technology.
You can find many presentations and whitepapers with practical test/simulation data especially with Focus on milimeter wave Radio Access Network.
No technical information is mentioned in this article, but based on what they have done until 4G, it would be worth following up what Erricsson plans. You will see an interesting contrasts from the first two aricles coming out in around 2 years interval. I am not trying to criticise on anything... this is a kind of normal opinion/mentality changes for almost all revolutionary technology.
They claims that they achieved 10 Gbps throughput in 11 Ghz, 400 Mhz BW with 24 antenna.
Huawei released a couple of articles about their plan for future technology sometime around Mar, 2012. Almost no detailed technical information is mentioned in these articles, but you can at least have some 'feeling' about what they intend to do.
Even though the WiFi (mainly based on IEEE specification) would not be exactly same as Mobile communication technology (mainly based on 3GPP specifiction), nobody would deny the fact that these two big bodies has been influencing each other for a long time. (Think about.. OFDM based WiFi --> WiMax --> LTE). Recently (as of July 2013), a lot of discussions are going on about 802.11ac which claim to support over 1Gb data rate and we already see some chipsets and real implementations are coming out.
Actually I would not call this as 5G. Technically I should call this as 'final target of 4G' which is targeted for 1 Gbps data rate. But I put this on this page because it shows a real demo (even though it is physical layer only and in very short distance) and I think this will be an important building block of next generation communication as well.
At least as of now (May 2013), it seems these material are most technical on the future technology.
You would get the most concrete idea on 3G at least as of now (June 2013).
This company released a test bed for Massive MIMO