These are the announced mobile market acquisitions that have mattered the most -- so far -- in 2012.

1. SoftBank-Sprint: This proposed US$20.1 billion acquisition of 70 percent of Sprint Corp. (NYSE: S) by Japan's SoftBank Corp. would create the world's third-largest wireless carrier. It's also likely to bolster the deployment of a 4G network based on Long Term Evolution Time Division Duplex (LTE TDD) technology, using Clearwire's 2.6GHz spectrum, as Sprint has once again taken majority control over its long-time 4G partner. (See Softbank to Pay $20B for 70% Sprint Stake and Sprint Buys Back Controlling Stake in Clearwire.)

2. T-Mobile-MetroPCS: The proposed $1.5 billion merger between T-Mobile US Inc. and MetroPCS Inc. (NYSE: PCS) could reshape the U.S. wireless scene by creating the country's largest pay-as-you-go carrier, which should be able blanket American cities with 4G Long Term Evolution (LTE) in 2013 and beyond. The reverse stock-split could also provide T-Mobile's German parent, Deutsche Telekom AG (NYSE: DT), with a magenta-lit exit from the American market. (See T-Mobile, MetroPCS to Merge and Is MetroPCS DT's Magenta Exit?)

3. Facebook-Instagram: The $1 billion valuation of the mobile photo-sharing startup by Facebook turned heads in April. The mobile social bubble is a little deflated now, following the relative failure of Facebook's IPO, but this acquisition still sets the bar for those looking to buy their way in to the mobile social applications market. (See Oh Snap! Facebook to Buy Instagram for $1B and Facebook's Future in Mobile.)

4. Ericsson-BelAir: Ericsson AB (Nasdaq: ERIC)'s purchase of BelAir Networks Inc. in February showed that carrier Wi-Fi hot zones have gone mainstream. Not only did Ericsson get its hands on BelAir's technology, it also landed some tasty carrier Wi-Fi deployments with operators such as AT&T Inc. (NYSE: T). (See Ericsson Adds Wi-Fi With BelAir Buy and Ericsson Gets Busy With BelAir .)

5. Qualcomm-DesignArt: Qualcomm Inc. (Nasdaq: QCOM) crashed into the LTE small-cell market in August with a deal to buy DesignArt Networks for up to $140 million. The CDMA giant also grabbed backhaul technology in the buy-up. (See Qualcomm Snaps Up Small Cell SoC Designer.)Postscript: The dark stars of M&A
Arguably, the failure of the merger between AT&T and T-Mobile in December 2011 has shaped the carrier M&A scene this year as much as any successful transaction: If AT&T had won over the Federal Communications Commission (FCC) and Antitrust Division of the U.S. Department of Justice objections, then T-Mobile wouldn't be linked with MetroPCS right now. And it's possible that Verizon Wireless may have been encouraged to try and swallow some smaller rivals if the AT&T merger had been approved. (see AT&T Drops Bid to Acquire T-Mobile.)

The jury is also currently out on the wisdom of Google (Nasdaq: GOOG) buying Motorola Mobility in a bid to create an Android powerhouse. The handset maker appears to be one of the factors dragging on Google's bottom line in its third-quarter results. (See Motorola Mobility Sinks Google's Earnings.) — Dan Jones, Site Editor, Light Reading Mobile