There are many ways to invest in the mobile space. Fortunately for Foolish investors, you don't have to pick a winner in the handset wars or even invest in the strongest wireless network providers.

We asked three Motley Fool contributors to present their best stock picks in the mobile sector, and none of these picks would fit in the obvious mobile categories listed above. Instead, they suggested smartphone chip designer Qualcomm (QCOM -0.51%), cell tower operator American Tower (AMT 0.12%), and mobile-friendly microblogging service Twitter (TWTR).

Read on to see what makes these unconventional picks more attractive than the usual mobile suspects.

Qualcomm CEO Steve Mollenkopf has many reasons to smile. So do his investors, according to Fool contributor Alex Planes. Image source: Qualcomm.

Alex Planes (Qualcomm): Our three Foolish perspectives couldn't be more different, and to start off this discussion, I've chosen leading mobile chipmaker, Qualcomm, as my top stock for the space.

Qualcomm's mobile dominance has been obvious for years, and it shows little signs of eroding. This is due in no small part to its valuable patent trove, which holds anywhere from 8% to 21% of the "essential" patents on LTE (commonly known as 4G) network technology, depending on whose data you use. Few companies have a larger share of essential LTE patents and by some counts, Qualcomm is the overall leader in standards-essential patents on this next-generation wireless technology.

Owning essential patents not only gives Qualcomm a leg up when it comes to developing its own wireless chips, it also pulls in billions of dollars in revenue every year. The company earned $7.9 billion in revenue from licensing agreements in its 2014 fiscal year and has made $22.4 billion in total licensing revenue over the past three fiscal years. Sixty-four percent of that total licensing revenue has flowed into research and development spending at the company. That's the ultimate virtuous cycle -- licensing revenue funds research into critical new wireless technologies, which will ultimately produce more licensing revenue.

Qualcomm's wireless chip leadership is also well known. The company controls two-thirds of the cellular baseband chip market, and no other competitor holds more than 15% of that market. Qualcomm also leads the market in integrated applications processors with graphics processing units with a 42% share, and it accounted for 53% of the overall mobile processor market by revenue earlier this year.

So why should you consider Qualcomm when its stock has been in the dumps all year? Just look at this chart:

QCOM Revenue (TTM) Chart

QCOM Revenue (TTM) data by YCharts.

Qualcomm's P/E ratio is near its all-time low, but all of its three fundamental metrics have outpaced share gains over the past five years. That sort of situation often sets up moribund large caps for a rebound, and Qualcomm is far from fading when it comes to its top and bottom lines. There is still plenty of upside left in 4G as well -- no country in the world besides South Korea had more than 21% of its population connected to 4G LTE networks at the end of 2013.

Anders Bylund (American Tower): The mobile space is large and varied, but the wireless industry simply doesn't work without the tower managers. That's why any investment in this industry is a simple bet on continued demand for radio-signal services. And unlike the cutthroat competitive landscapes in handsets and carrier operation, it's actually pretty easy to identify the best stock in this submarket. American Tower's growth prospects stand head and shoulders above other alternatives among wireless tower operators. 

Image source: Author.

The U.S. tower space is fairly well defined and has already been divided between a handful of major operators. But American Tower runs its business better than its largest rivals, producing wider profit margins and returns on equity. Management uses the excess capital generated by this superior execution to pursue new growth opportunities in developing markets.

For example, American Tower just agreed to buy 6,500 sites in Brazil for $1.2 billion and followed up with a $1.1 billion deal for 4,800 towers in Nigeria. That's a 16% increase in global tower sites, all announced in the span of three days.

Look, I don't know whether Apple or Huawei will dominate the handset market in any particular territory -- let alone worldwide. But I do know American Tower runs a hyper-efficient business model that will remain relevant as long as wireless signals play a part in the global economy, and nobody is going after high-growth expansion opportunities like this company does.

American Tower is hungry for growth, armed with fantastic fundamentals, and simply the safest high-growth bet on mobile communications on the market today. That's why I own the stock myself.

Image source: Twitter.

Joe Tenebruso (Twitter): Twitter is a mobile stock with tremendous upside. Unlike social network competitors such as Facebook that had to transition their platforms from desktop to mobile, Twitter was born mobile. Its 140-character maximum for the billions of messages that flow through its network is perfectly designed for today's fast-paced and increasingly mobile world.

That's why I expect advertising dollars to continue to fall into Twitter's waiting arms. Dollars follow audience, and Twitter's user growth -- and, importantly, its global reach beyond its own application -- remains on an upward trend. With multiple new initiatives under way to better target both registered users and non-logged-in visitors, as well as new and previous users, I believe we'll see a strong improvement in Twitter's ability to monetize its massive audience.

However, it's important to understand that Twitter is a premium-priced business with a volatile stock price. Shares are down nearly 40% year-to-date, yet they still trade at more than 100 times analyst estimates for 2015. Make no mistake, an investment in Twitter today requires a belief that the company will grow into its valuation and deliver the tremendous revenue and earnings boosts necessary to provide adequate returns to investors from this point forward. I believe the power of Twitter's network and its opportunities warrant taking that risk. Do you? Let us know in the comments section below.