Ransack search multiple words

# models/user.rb

class User < ActiveRecord::Base
  has_secure_password
  attr_accessible :email, :password, :password_confirmation, :profile_attributes, :group_ids


  has_one :profile, :inverse_of => :user
  accepts_nested_attributes_for :profile
end

# models/profile.rb
class Profile < ActiveRecord::Base
 attr_accessible :first_name, :last_name, :phone_fix, :phone_mobile, :user_id, :zip_code
 belongs_to :user, :inverse_of => :profile
end

# controllers/users_controller.rb
class UsersController < ApplicationController
def index
    @q = User.joins(:profile).search(params[:q])

    @users = @q.result.paginate(:per_page =>10, :page => params[:page])

    respond_to do |format|
      format.html # index.html.erb
      format.json { render json: @users }
    end
  end

  def search
    @q = User.joins(:profile).search(params[:q])
    @users = @q.result.paginate(:per_page => 10, :page => params[:page])
    render "index"
  end
end

# views/users/index.html.erb (search form only)
<%= search_form_for @q, url: search_users_path, method: 'post', id: 'users-search-form' do |f| %>
        <%= f.text_field :profile_last_name_or_profile_first_name %>
    <%= f.submit %>
<% end %>